Added macros for Haskell Cabal

[DataDrake]

These macros should make it considerably faster/easier to package haskell libraries and development binaries:

• cabal_configure Create a user package database, rebuild the package.cache for ghc, then configure for a dynamically linked build
• cabal_build Compile the source with %JOBS% processes
• cabal_install Install the outputs to $installdir
• cabal_register Generate the package.conf.d entry, install it, then wipe out any static libs.

Caveats:

1. Must always install ghc and haskell-cabal-install for the macros to work.
2. cabal_register always removes static libs
3. cabal_register assumes library is prefixed with haskell-