------------------------
	Fix a type-invariant bug
	------------------------

We need to call Type.mkGenTyConApp from Type.mkAppTy, in
case there's a partially applied type synonym.  Explanation
with Type.mkAppTy.  All part of GHC's rather liberal treatment
of type synonyms.

Shown up by a program from Ralf Laemmel:

	type Generic i o = forall x. i x -> o x
	type Id x = x
	comb :: Generic Id Id

Test is typecheck/should_compile/tc149.hs