[Comment parsing] Add support for recognizing
\headerfile command and representing it in an xml
document. Patch reviewed by Dmitri Gribenko.
// rdar://12397511


git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@174109 91177308-0d34-0410-b5e6-96231b3b80d8
Update the tests.

This update coincides with r174110. That change ordered the attributes
alphabetically.


git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@174111 91177308-0d34-0410-b5e6-96231b3b80d8
Escape backslash in the comment.


git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@174112 91177308-0d34-0410-b5e6-96231b3b80d8
Comment parsing: add more comments to CommentCommands.td

I hope the ASCII art delimiters are OK, since they group *groups* of commands --
that is really helpful.


git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@174114 91177308-0d34-0410-b5e6-96231b3b80d8