Adding options for ghc-core-create-core

Hi. This single commit just add possibility to specify additional options when we call ghc for core output. Default behaviour isn't changed.
Also, I guess, `ghc-core-clean-region' becomes useless a bit, since we can specify "-dsuppress-module-prefixes" in options list or some other [suppress option][sup-opts].

[sup-opts]: http://www.haskell.org/ghc/docs/latest/html/users_guide/options-debugging.html#supression