* Make it so that recursive newtype declarations don't send
  GHC into an infinite loop.

	newtype T = MkT T

  This happened because Type.repType looked throught newtypes,
  and that never stopped!  Now TcTyDecls.mkNewTyConRep does the job
  more carefully, and the result is cached in the TyCon itself.


* Improve the handling of type signatures & pragmas.  Previously a
  mis-placed (say) SPECIALISE instance pragmas could be silently
  ignored.


Both these changes involved moving quite a lot of stuff between modules.