Build with integer-simple

[basvandijk]

Some users of scientific require to build the package with integer-simple. After I switched to integer-logarithms I lost this capability.

Could you add integer-simple support to integer-logarithms? Let me know if you need help.

[phadej]

Currently building ghc with integer-simple

[basvandijk]

Ok. I'm doing the same :) and created a PR for nixpkgs in the process for getting a GHC with integer-simple.

[phadej]

@basvandijk there's a PR, and tests pass locally (there's no integer-simple ghc in hvr-ppa, so cannot test on travis). But it would be great to verify with a bit larger package sets (e.g. run scientific and aeson tests?). If it's not too difficult with your nix setup, it would be great!