Add haddock path to cfg/system.config.in.
Add haddock path to cfg/system.config.in.

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