ghc-mod and FFI

Hi,

recently I run into an issue using ghc-mod, as described here:
https://github.com/kazu-yamamoto/ghc-mod/issues/75
In summary, ghc-mod fails if the source file contains a `foreign'
declaration. I played around a bit, but I have no experience with the
GHC API, so any help is appreciated!

Thanks,
Bernhard