Remove references to response file argument in CommandLine.rst

[kastiglione]

Summary

The documentation refers to a boolean that controls whether response files are
handled, but this is incorrect. Since r165535, response files are always
enabled.

llvm/trunk/docs/CommandLine.rst

 Response files
 ^^^^^^^^^^^^^^
 
 Some systems, such as certain variants of Microsoft Windows and some older
 Unices have a relatively low limit on command-line length. It is therefore
 customary to use the so-called 'response files' to circumvent this
 restriction. These files are mentioned on the command-line (using the "@file")
 syntax. The program reads these files and inserts the contents into argv,
-thereby working around the command-line length limits. Response files are
-enabled by an optional fourth argument to `cl::ParseEnvironmentOptions`_ and
-`cl::ParseCommandLineOptions`_.
+thereby working around the command-line length limits.
 
 Top-Level Classes and Functions
 -------------------------------
 
 Despite all of the built-in flexibility, the CommandLine option library really
 only consists of one function `cl::ParseCommandLineOptions`_) and three main
 classes: `cl::opt`_, `cl::list`_, and `cl::alias`_.  This section describes
 these three classes in detail.

 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 The ``cl::ParseCommandLineOptions`` function is designed to be called directly
 from ``main``, and is used to fill in the values of all of the command line
 option variables once ``argc`` and ``argv`` are available.
 
 The ``cl::ParseCommandLineOptions`` function requires two parameters (``argc``
 and ``argv``), but may also take an optional third parameter which holds
-`additional extra text`_ to emit when the ``-help`` option is invoked, and a
-fourth boolean parameter that enables `response files`_.
+`additional extra text`_ to emit when the ``-help`` option is invoked.
 
 .. _cl::ParseEnvironmentOptions:
 
 The ``cl::ParseEnvironmentOptions`` function
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 The ``cl::ParseEnvironmentOptions`` function has mostly the same effects as
 `cl::ParseCommandLineOptions`_, except that it is designed to take values for
 options from an environment variable, for those cases in which reading the
 command line is not convenient or desired. It fills in the values of all the
 command line option variables just like `cl::ParseCommandLineOptions`_ does.
 
 It takes four parameters: the name of the program (since ``argv`` may not be
 available, it can't just look in ``argv[0]``), the name of the environment
-variable to examine, the optional `additional extra text`_ to emit when the
-``-help`` option is invoked, and the boolean switch that controls whether
-`response files`_ should be read.
+variable to examine, and the optional `additional extra text`_ to emit when the
+``-help`` option is invoked.
 
 ``cl::ParseEnvironmentOptions`` will break the environment variable's value up
 into words and then process them using `cl::ParseCommandLineOptions`_.
 **Note:** Currently ``cl::ParseEnvironmentOptions`` does not support quoting, so
 an environment variable containing ``-option "foo bar"`` will be parsed as three
 words, ``-option``, ``"foo``, and ``bar"``, which is different from what you
 would get from the shell with the same input.