Fix more interface-reading bugs:
-- Qualtypes were not being generated from DICTAPs for overloaded
   non-class values.  New function dictapsToQualtype to handle this.
-- Incorrect construction of constructor result type in startGHCDataDecl
   for parameterised types eg   Just :: a -> Maybe a.

Changed meaning of DICTAP, so that the construction is
  ap(DICTAP, (QConId, Type))  rather than
  ap(DICTAP, (QConId, [Type])).  Will have to undo this if we want
                                 to support multiparam type classes.