hackage-packages.nix: update Haskell package set

This update was generated by hackage2nix v20150922-27-g14f44af using the following inputs:

  - Nixpkgs: https://github.com/NixOS/nixpkgs/commit/296838820efbbdc15eb6578aca5c56c585e0e8eb
  - Hackage: https://github.com/commercialhaskell/all-cabal-hashes/commit/cbced5bc0e764a895b04245021b2156331927737
  - LTS Haskell: https://github.com/fpco/lts-haskell/commit/4622b913dcfa6d442d875c8604a87cc79884f74c
  - Stackage Nightly: https://github.com/fpco/stackage-nightly/commit/05c38f5cda81680f98e751a37a66f5c1f2730789