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/f90e42f3826a522f4c182a65f1e54ef15de87c2d
  - Hackage: https://github.com/commercialhaskell/all-cabal-hashes/commit/96af3096ee3302efe0d4a4fa16519546b077b436
  - LTS Haskell: https://github.com/fpco/lts-haskell/commit/71e581f8e49ab6210581b4fac45ec18445e1fa93
  - Stackage Nightly: https://github.com/fpco/stackage-nightly/commit/97a0714af749868ff5b21f427cca523d59637360