Add comments.
Add comments.

sdiehl/ghc,snowleopard/shaking-up-ghc,sdiehl/ghc,sdiehl/ghc,bgamari/shaking-up-ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,quchen/shaking-up-ghc,izgzhen/hadrian,snowleopard/hadrian