use showRichTokenStream' instead of GHC.showRichTokenStream

This is because the GHC behaviour has been fixed in version 7.8.3,
showRichTokenStream' is the GHC 7.8.3 one, to allow tests to pass for
the older compilers
More working in of the GHC 7.8.3 AST. Now to fill in the undefineds and
get it to work