Add Haddock-Options field to Cabal package description

(Imported from [Trac #936](http://hackage.haskell.org/trac/hackage/ticket/936), reported by guest on 2012-04-01)

Currently when running 'runhaskell Setup haddock' I can pass options to Haddock with the --haddock-option and --haddock-options option. I would like to add some options in a Cabal description file analogously to the GHC-Options fields and others.