Add haddock build targets.
Add haddock build targets.

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