Add ghcjs support to haskell-devscripts (http://anonscm.debian.org/darcs/pkg-haskell/haskell-devscripts)

#1Use ghc --info instead of ghc -e

In Dh_Haskell.sh the cpu and os functions are implemented by running ghc -e, which requires ghci. Because this is not available on all architectures, the functions instead should parse the output of ghc --info.