[Haskell] Cabal support for djinn

Hi Lennart, I really like djinn and decided to write a quick darcs patch for it so one can use cabal (http://haskell.org/cabal/) for building it. As I couldn't find any license informations, I inserted "AllRightsReserved" as the license field. Feel free to change that! I'd love to see it being released under a GPL or BSD style license, but that's just my opinion. Henning