add ghc-deps.sh for hash rpm metadata and add ghc_pkg_obsoletes
    
    - add ghc-deps.sh for ghc package hash rpm metadata provides and requires
    - turn on hash provides and disable debuginfo by default
    - make shared and hscolour default
    - use without_shared and without_hscolour to disble them
    - add ghc_pkg_obsoletes for obsoleting old packages
    - use ghcpkgbasedir
    - always obsolete -doc packages, but keep -o for now for backward compatibility