hackage-packages.nix: update Haskell package set

This update was generated by hackage2nix v20151217-2-g519e0a9 using the following inputs:

  - Nixpkgs: https://github.com/NixOS/nixpkgs/commit/2ed14d2303783870523dae5300b89a4082fe5f6b
  - Hackage: https://github.com/commercialhaskell/all-cabal-hashes/commit/53c15ee9e31d2532bc6e8fc9fd85fb21f5de2303
  - LTS Haskell: https://github.com/fpco/lts-haskell/commit/b668f53a86774535a58fdc7ae45ed757fcc597cc
  - Stackage Nightly: https://github.com/fpco/stackage-nightly/commit/ec9500b675b55f53ad1153282cdd772098a5cdbe