hackage-packages.nix: update Haskell package set

This update was generated by hackage2nix v20150922-35-g816abb5 using the following inputs:

  - Nixpkgs: https://github.com/NixOS/nixpkgs/commit/1df25a5f13020f59fea6ddf7c52dd006884d635d
  - Hackage: https://github.com/commercialhaskell/all-cabal-hashes/commit/cb4ec9770f65cadb4f636340c599ad0da83927ae
  - LTS Haskell: https://github.com/fpco/lts-haskell/commit/71e581f8e49ab6210581b4fac45ec18445e1fa93
  - Stackage Nightly: https://github.com/fpco/stackage-nightly/commit/6fbe569da0dead6f4043b6c01dda19457cd0fd7e