major updates for ghc-6.12, package.conf.d, and shared libraries
    - add shared support to cabal_configure, ghc_gen_filelists
    - version ghcdocdir
    - replace ghc_gen_scripts, ghc_install_scripts, ghc_register_pkg,
        ghc_unregister_pkg with cabal_pkg_conf
    - allow (ghc to) override ghc_version