[clang-tidy] Update documentation

[deniz]

Summary

We have 2 scripts add_new_check.py and rename_check.py to bootstrap a new check creation. There is also clang-query to aid with the matcher creation. These were not mentioned in the current document, add them so it's available to the masses.

[alexfh]

Looks good. Thanks!

[alexfh]

BTW, do you have commit access or you need someone to commit the patch for you?

[deniz]

I unfortunately don't have commit rights, could you please commit the patch for me?

Thanks!

clang-tools-extra/trunk/docs/clang-tidy/index.rst

 ================
 
 :program:`clang-tidy` has several own checks and can run Clang static analyzer
 checks, but its power is in the ability to easily write custom checks.
 
 Checks are organized in modules, which can be linked into :program:`clang-tidy`
 with minimal or no code changes in clang-tidy.
 
+``add_new_check.py`` is a script to automate the process of adding a new check,
+it will create the check, update the CMake file and create a test.
+
+``rename_check.py`` does what the script name suggest, renames an existsing
+check.
+
 Checks can plug the analysis on the preprocessor level using `PPCallbacks`_ or
 on the AST level using `AST Matchers`_. When an error is found, checks can
 report them in a way similar to how Clang diagnostics work. A fix-it hint can be
 attached to a diagnostic message.
 
+To find out what matchers you can add, we recommend using :program:`clang-query`,
+it's a tool is for interactive exploration of the Clang AST using AST matchers.
+
 The interface provided by clang-tidy makes it easy to write useful and precise
 checks in just a few lines of code. If you have an idea for a good check, the
 rest of this document explains how to do this.
 
 .. _AST Matchers: http://clang.llvm.org/docs/LibASTMatchers.html
 .. _PPCallbacks: http://clang.llvm.org/doxygen/classclang_1_1PPCallbacks.html