[Haskell-cafe] Haxr doesn't compile from cabal (HTTP > 4000 breaks it)

Most breakage caused by new HTTP package is due to the renaming from Response to Response_String and Request to Request_String. I think it was not a good idea to do that. There could have well be two types named Response from different modules, one with a type parameter and the other one without. Or the parametrized variant could have be named ResponseGeneric or so. That would have allowed packages to work both with version 3001 and 4000.