[PATCH] Emit Clang version information into .comment section (CodeGen's part of implementation) [PART 2A]

[Katya Romanova]

  Hi Rafael,
  I don't have a commit access.  Please don't commit yet, since MC part needs to be committed first (otherwise we will break the build). I am working on MC part changes now.
  Katya.

http://llvm-reviews.chandlerc.com/D1806