the patch for  augmenting the ghc settings file to help decouple CPP from the C Compiler choice now works, on both the configure/autconf and ghc builds and uses it correctly fronts! 

It also results in removing the cRAWCPP variable from Config.hs, which I think is a good thing! (removes a hack / potential source of cruft).

I'd love some feedback/ suggestions for this patch please. 
I'd also like to thank Peter Trommler for helping me debug / fix up my incorrect m4/autoconf component of the patch. 

the point of this patch is to make it very easy to provide a GHC that by default uses a different program for "Haskell CPP" than for compiling C code (which can only be done currently via a wrapper script hack thats a bit fragile, or via passing -pgmP everywhere! )

thanks

-Carter