hackage-packages.nix: update Haskell package set

This update was generated by hackage2nix v20160308-3-g8057d11 using the following inputs:

  - Nixpkgs: https://github.com/NixOS/nixpkgs/commit/3b6870536f4ba989ef2b3f6d919564d5a5d3faac
  - Hackage: https://github.com/commercialhaskell/all-cabal-hashes/commit/f6dcb81d2a28b1419ef4a4b6513276e52c75f6bb
  - LTS Haskell: https://github.com/fpco/lts-haskell/commit/6bcb171af74b3bcce09d9ba8da3c2ef819232dcc
  - Stackage Nightly: https://github.com/fpco/stackage-nightly/commit/fbf2e48e585f4323b603c9e72e8b925cfe0f5724