hackage-packages.nix: update Haskell package set

This update was generated by hackage2nix v20150922-11-gaf50139 using the following inputs:

  - Nixpkgs: https://github.com/NixOS/nixpkgs/commit/2ff1ebc619037a2978dc4f88643e9347952ee261
  - Hackage: https://github.com/commercialhaskell/all-cabal-hashes/commit/6f52d0a4a2525e73b6eff868376843048def23c6
  - LTS Haskell: https://github.com/fpco/lts-haskell/commit/c5f1e507cd73fda2551f36492eb1d0c3f7b65f3a
  - Stackage Nightly: https://github.com/fpco/stackage-nightly/commit/9351235d2841a12fd6e99e9b12464bbfca7834ae