Unlines fix

Old definition was `intercalate "\n"`, new definition is from http://www.haskell.org/ghc/docs/latest/html/libraries/base-4.6.0.1/src/Data-List.html#line-1086.  The only difference is the newline at the end.

It seems like it should be possible to write a utility to extract the fay prelude from the ghc prelude.  That'd be cool!  Maybe no point at this time though