Frown: c2hs parser

I have been working on a Frown version of the c2hs C Parser. This is the initial check-in.

The code compiles though the parser has no actions, so it does not build a parse tree. The lexer is also incomplete - white space is the most obvious omission. Getting the code to compile has been over 4 days work, so I'm commiting this draft now.

GHC is taxed by the code that Frown generates. In particular Frown's compact format will not compile even though the code is smaller - the absence of type signatures on such a large file makes trouble for GHC's type inferencing.