[PATCH] Option parsing: support case-insensitive option matching.

[Reid Kleckner]

  LGTM

  There's still a circular dependence here that you're avoiding with inline functions, but the only way to avoid it is by putting this string comparison into Support, which I don't like.

http://llvm-reviews.chandlerc.com/D1485

BRANCH
  ignore-case

ARCANIST PROJECT
  llvm