hackage-packages.nix: update Haskell package set

This update was generated by hackage2nix v20150922-46-gf1bbc76 using the following inputs:

  - Nixpkgs: https://github.com/NixOS/nixpkgs/commit/7c559e1c0f827ed1788a646f4df923993fc49354
  - Hackage: https://github.com/commercialhaskell/all-cabal-hashes/commit/49a7fb0a6f5f158ceee82cac53a8e006b53a7d7a
  - LTS Haskell: https://github.com/fpco/lts-haskell/commit/57dab1c9974199e11130c3da70ffa31480a9ca37
  - Stackage Nightly: https://github.com/fpco/stackage-nightly/commit/ecefc78ca3a23e0cce1ac04ed43e28746d56aa2e