Major Haskell packages overhaul.

Several changes, some highlights:

  * Structure of haskell-packages.nix updated. It's now easier to
    select different default versions of packages for different
    versions of GHC.

  * GHC 7.0.2 is now default.

  * Haskell Platform 2011.2.0.0 has been added and is now default.

  * Several packages have been updated
    (gtk2hs, gitit, xmonad, darcs, ...).

  * Some old packages have been removed.

svn path=/nixpkgs/trunk/; revision=26288

pkgs/development/libraries/haskell/mtl/1.1.1.1.nix

@@ -0,0 +1,11 @@
+{cabal}:
+
+cabal.mkDerivation (self : {
+  pname = "mtl";
+  version = "1.1.1.1"; # version of mtl1 compatible with ghc7
+  sha256 = "157gbrgrg0l9r72nq45dkach53yncysif4qglsaql28g37djc4x6";
+  meta = {
+    description = "Monad transformer library";
+  };
+})  
+

pkgs/development/libraries/haskell/mtl/2.0.1.0.nix

@@ -0,0 +1,12 @@
+{cabal, transformers}:
+
+cabal.mkDerivation (self : {
+  pname = "mtl";
+  version = "2.0.1.0"; # Haskell Platform 2011.2.0.0
+  sha256 = "1w6jpzyl08mringnd6gxwcl3y9q506r240vm1sv0aacml1hy8szk";
+  propagatedBuildInputs = [transformers];
+  meta = {
+    description = "Monad transformer library";
+  };
+})  
+