fsharp: 3.0 -> 3.1, and attempt to fix build

Hopefully this fix will appease hydra - the distributed autogen.sh
script is annoying.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
Merge branch 'fsharp' of git://github.com/thoughtpolice/nixpkgs

fsharp: 3.0 -> 3.1, and attempt to fix build