[PATCH] MC: handle ParseDirective properly

[Saleem Abdulrasool]

  The individual ones can probably be updated to return void (Ill try to do that as appropriate).  Unfortunately, the generic parser must be informed if it needs to process the directive or not, so I don't see how it would be possible to change that to avoid use of the return type to indicate that.

http://llvm-reviews.chandlerc.com/D2410