Oops, the underline was too short for sphinx to like.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@221993 91177308-0d34-0410-b5e6-96231b3b80d8

docs/LanguageExtensions.rst

@@ -110,7 +110,7 @@ the same name.  For instance, ``__cxx_rvalue_references__`` can be used instead
 of ``cxx_rvalue_references``.
 
 ``__has_cpp_attribute``
--------------------
+-----------------------
 
 This function-like macro takes a single argument that is the name of a
 C++11-style attribute. The argument can either be a single identifier, or a