Update references to Discourse instead of the mailing lists.

[tonic]

Summary

Update the references to the old Mailman mailing lists to point to Discourse forums.

[aaron.ballman]

LGTM with some minor corrections. Thank you for this!

clang/docs/ExternalClangExamples.rst

21–23

clang/www/get_involved.html

39

[tonic]

Fix typos.

clang/docs/ExternalClangExamples.rst

 Clang's library-based design is deliberately aimed at facilitating use by
 external projects, and we are always interested in improving Clang to
 better serve our external users. Some typical categories of applications
 where Clang is used are:
 
 - Static analysis.
 - Documentation/cross-reference generation.
 
-If you know of (or wrote!) a tool or project using Clang, please send an
-email to Clang's `development discussion mailing list
-<https://lists.llvm.org/mailman/listinfo/cfe-dev>`_ to have it added.
+If you know of (or wrote!) a tool or project using Clang, please post on 
+`the Discourse forums (Clang Frontend category)
+<https://discourse.llvm.org/c/clang/6>`_ to have it added.
 (or if you are already a Clang contributor, feel free to directly commit
 additions). Since the primary purpose of this page is to provide examples
 that can help developers, generally they must have code available.
 
 List of projects and tools
 ==========================
 
 `<https://github.com/Andersbakken/rtags/>`_

clang/docs/InternalsManual.rst

 correctly.  If it is ever incorrect, the front-end may get confused and die.
 The reason for this is that the notion of the "spelling" of a ``Token`` in
 Clang depends on being able to find the original input characters for the
 token.  This concept maps directly to the "spelling location" for the token.
 
 ``SourceRange`` and ``CharSourceRange``
 ---------------------------------------
 
-.. mostly taken from https://lists.llvm.org/pipermail/cfe-dev/2010-August/010595.html
+.. mostly taken from https://discourse.llvm.org/t/code-ranges-of-tokens-ast-elements/16893/2
 
 Clang represents most source ranges by [first, last], where "first" and "last"
 each point to the beginning of their respective tokens.  For example consider
 the ``SourceRange`` of the following statement:
 
 .. code-block:: text
 
   x = foo + bar;

clang/docs/OpenCLSupport.rst

 
 .. _opencl_experimenal:
 
 Experimental features
 =====================
 
 Clang provides the following new WIP features for the developers to experiment
 and provide early feedback or contribute with further improvements.
-Feel free to contact us on `cfe-dev
-<https://lists.llvm.org/mailman/listinfo/cfe-dev>`_ or file `a GitHub issue
+Feel free to contact us on `the Discourse forums (Clang Frontend category)
+<https://discourse.llvm.org/c/clang/6>`_ or file `a GitHub issue
 <https://github.com/llvm/llvm-project/issues/new>`_.
 
 .. _opencl_experimental_cxxlibs:
 
 C++ libraries for OpenCL
 ------------------------
 
 There is ongoing work to support C++ standard libraries from `LLVM's libcxx

clang/docs/OpenMPSupport.rst

 
 
 .. _OpenMP implementation details:
 
 OpenMP 5.0 Implementation Details
 =================================
 
 The following table provides a quick overview over various OpenMP 5.0 features
-and their implementation status. Please contact *openmp-dev* at
-*lists.llvm.org* for more information or if you want to help with the
+and their implementation status. Please post on the
+`Discourse forums (Runtimes - OpenMP category)`_ for more 
+information or if you want to help with the
 implementation.
 
 +------------------------------+--------------------------------------------------------------+--------------------------+-----------------------------------------------------------------------+
 |Category                      | Feature                                                      | Status                   | Reviews                                                               |
 +==============================+==============================================================+==========================+=======================================================================+
 | loop                         | support != in the canonical loop form                        | :good:`done`             | D54441                                                                |
 +------------------------------+--------------------------------------------------------------+--------------------------+-----------------------------------------------------------------------+
 | loop                         | #pragma omp loop (directive)                                 | :part:`worked on`        |                                                                       |

 +------------------------------+--------------------------------------------------------------+--------------------------+-----------------------------------------------------------------------+
 
 
 OpenMP 5.1 Implementation Details
 =================================
 
 The following table provides a quick overview over various OpenMP 5.1 features
 and their implementation status, as defined in the technical report 8 (TR8).
-Please contact *openmp-dev* at *lists.llvm.org* for more information or if you
-want to help with the implementation.
+Please post on the 
+`Discourse forums (Runtimes - OpenMP category)`_ for more 
+information or if you want to help with the
+implementation.
 
 +------------------------------+--------------------------------------------------------------+--------------------------+-----------------------------------------------------------------------+
 |Category                      | Feature                                                      | Status                   | Reviews                                                               |
 +==============================+==============================================================+==========================+=======================================================================+
 | atomic                       | 'compare' clause on atomic construct                         | :good:`done`             | D120290, D120007, D118632, D120200, D116261, D118547, D116637         |
 +------------------------------+--------------------------------------------------------------+--------------------------+-----------------------------------------------------------------------+
 | atomic                       | 'fail' clause on atomic construct                            | :part:`worked on`        |                                                                       |
 +------------------------------+--------------------------------------------------------------+--------------------------+-----------------------------------------------------------------------+

 | task                         | inoutset in depend clause                                    | :none:`unclaimed`        |                                                                       |
 +------------------------------+--------------------------------------------------------------+--------------------------+-----------------------------------------------------------------------+
 | task                         | nowait clause on taskwait                                    | :part:`worked on`        |                                                                       |
 +------------------------------+--------------------------------------------------------------+--------------------------+-----------------------------------------------------------------------+
 
 OpenMP Extensions
 =================
 
-The following table provides a quick overview over various OpenMP
+The following table provides a quick overview over various OpenMP 
 extensions and their implementation status.  These extensions are not
 currently defined by any standard, so links to associated LLVM
 documentation are provided.  As these extensions mature, they will be
-considered for standardization.  Please contact *openmp-dev* at
-*lists.llvm.org* to provide feedback.
+considered for standardization. Please post on the
+`Discourse forums (Runtimes - OpenMP category)`_ to provide feedback. 
 
 +------------------------------+-----------------------------------------------------------------------------------+--------------------------+--------------------------------------------------------+
 |Category                      | Feature                                                                           | Status                   | Reviews                                                |
 +==============================+===================================================================================+==========================+========================================================+
 | atomic extension             | `'atomic' strictly nested within 'teams'                                          | :good:`prototyped`       | D126323                                                |
 |                              | <https://openmp.llvm.org/docs/openacc/OpenMPExtensions.html#atomicWithinTeams>`_  |                          |                                                        |
 +------------------------------+-----------------------------------------------------------------------------------+--------------------------+--------------------------------------------------------+
 | device extension             | `'ompx_hold' map type modifier                                                    | :good:`prototyped`       | D106509, D106510                                       |
 |                              | <https://openmp.llvm.org/docs/openacc/OpenMPExtensions.html#ompx-hold>`_          |                          |                                                        |
 +------------------------------+-----------------------------------------------------------------------------------+--------------------------+--------------------------------------------------------+
+
+.. _Discourse forums (Runtimes - OpenMP category): https://discourse.llvm.org/c/runtimes/openmp/35

clang/docs/ReleaseNotes.rst

 A wide variety of additional information is available on the `Clang web
 page <https://clang.llvm.org/>`_. The web page contains versions of the
 API documentation which are up-to-date with the Git version of
 the source code. You can access versions of these documents specific to
 this release by going into the "``clang/docs/``" directory in the Clang
 tree.
 
 If you have any questions or comments about Clang, please feel free to
-contact us via the `mailing
-list <https://lists.llvm.org/mailman/listinfo/cfe-dev>`_.
+contact us on the Discourse forums (Clang Frontend category)
+<https://discourse.llvm.org/c/clang/6>`_.

clang/www/get_involved.html

 
 <h2>Contribute</h2>
 
 See the <a href="hacking.html">hacking</a> document for information on how
 to author patches.
 
 <h2>Follow what's going on</h2>
 
-<p>Clang is a subproject of the <a href="https://llvm.org">LLVM Project</a>, but
-has its own mailing lists because the communities have people with different
-interests.  The two clang lists are:</p>
+<p>Clang is a subproject of the <a href="https://llvm.org">LLVM Project</a>
+and has a Discourse forum and mailing list:</p>
 
 <ul>
 <li><a href="https://lists.llvm.org/mailman/listinfo/cfe-commits">cfe-commits
 </a> - This list is for patch submission/discussion.</li>
 
-<li><a href="https://lists.llvm.org/mailman/listinfo/cfe-dev">cfe-dev</a> -
-This list is for everything else Clang related (questions and answers, design
+<li><a href="https://discourse.llvm.org/c/clang/6">Clang Frontend Discourse forum</a> -
+This forum is for everything else Clang related (questions and answers, design
 discussions, etc).</li>
 
 </ul>
 
-<p>If you are interested in clang only, these two lists should be all
-you need.  If you are interested in the LLVM optimizer and code generator,
-please consider signing up for <a
-href="https://lists.llvm.org/mailman/listinfo/llvm-dev">llvm-dev</a> and <a
-href="https://lists.llvm.org/mailman/listinfo/llvm-commits">llvm-commits</a>
-as well.</p>
-
-
 <p>The most common way to talk with other developers on the project is through
-the <a href="https://lists.llvm.org/mailman/listinfo/cfe-dev">cfe-dev mailing
-list</a>.  The clang mailing list is a very friendly place and we welcome
-newcomers.  In addition to the cfe-dev list, a significant amount of design
+the <a href="https://discourse.llvm.org/c/clang/6">Clang Frontend Discourse forum
+</a>.  The clang forum is a very friendly place and we welcome
+newcomers.  In addition to the forum, a significant amount of design
 discussion takes place on the <a
 href="https://lists.llvm.org/mailman/listinfo/cfe-commits">cfe-commits mailing
 list</a>.  All of these lists have archives, so you can browse through previous
 discussions or follow the list development on the web if you prefer.</p>
 
-<p>You can also follow the <a href="http://planet.clang.org/">Planet Clang</a>
-community news feed which offers a window into the world, work and lives of
-Clang developers, contributors and the standards they implement.</p>
-
 <p>If you're looking for something to work on, check out our <a
 href="OpenProjects.html">Open Projects</a> page or look through the <a
 href="https://github.com/llvm/llvm-project/issues/">LLVM bug tracker</a>.</p>
 
 <h2 id="criteria">Contributing Extensions to Clang</h2>
 
 <p>Clang is designed to support experimentation,
 allowing programmers to easily extend the compiler to support great