hackage-packages.nix: update Haskell package set

This update was generated by hackage2nix v20150922-42-g3ca1747 using the following inputs:

  - Nixpkgs: https://github.com/NixOS/nixpkgs/commit/ad0723f0c71afc7b5e86eba1958aed0fd5761c95
  - Hackage: https://github.com/commercialhaskell/all-cabal-hashes/commit/c7478af457cffe9194a43314b6c0fded1546b275
  - LTS Haskell: https://github.com/fpco/lts-haskell/commit/8ec1fc34193fe53e8e257219cb2e4618f82cade5
  - Stackage Nightly: https://github.com/fpco/stackage-nightly/commit/e6bcfb640c367a777c0b398240fe58ef20d141c8