[PATCH] Expose the name of the checker producing each diagnostic message.

[Jordan Rose]

  Yes, this looks good!

  (Two possible ways to make the Optional change less wordy: use `*` for `getValue()`, and name the variable something else so that you don't have to qualify `CheckKind` with `MallocChecker::`.)

http://llvm-reviews.chandlerc.com/D2557

BRANCH
  svn

ARCANIST PROJECT
  clang