[WIP] Fix duplicate symbol error on Darwin

[adinapoli]

Fixes #18.

The problem stemmed from the fact that we had that _set_ridley_ifi_data symbol defined twice: one by inline-c as part of the quasi-quoter here and once in the relevant Network/Darwin.c file.

Now, due to the fact that the .c file was added to the c-sources section of the cabal manifest, that triggered the error. For now I have simply removed the relevant .c file from the repo and from the c-sources, and things still seem to work just fine, although I am puzzled on how: if I remember correctly inline-c works by generate C code on the fly in a way similar to this therefore I was still expecting the library to generate a .c file that I could later add to the c-sources, but this didn't happen.

I am temporarily marking the PR as WIP to make sure this is working only due to some cache artefacts on my system.

[coveralls]

Coverage remained the same at 37.821% when pulling 0826fae on adinapoli/issue-18 into e8daf02 on master.

[adinapoli]

@etherz10 I am going to merge this so we can test it out, and we can re-open in case of problems.