hackage-packages.nix: update Haskell package set

This update was generated by hackage2nix v20150922-18-g943a6d6 using the following inputs:

  - Nixpkgs: https://github.com/NixOS/nixpkgs/commit/b50d1833baf9a50c2afa5f0aa38a87c6eaf74b06
  - Hackage: https://github.com/commercialhaskell/all-cabal-hashes/commit/370eb30278fbb6c690a2b32fd2939365934b6415
  - LTS Haskell: https://github.com/fpco/lts-haskell/commit/0d493eae3616d7da684f1b6bf35709bc4408a5c0
  - Stackage Nightly: https://github.com/fpco/stackage-nightly/commit/6fbf34ed626be44ccc8e4ee3a7a24efd6a825f68