There are three bugs here, one serious

 * We were failing to tidy the type arguments in an IfTyConParent
   This is what was causing Trac #9190.

 * toIfaceTcArgs is careful to suppress kind arguments, but there
   was a clone, tidyToIfaceTcArgs in IfaceSyn which didn't.
   Now the latter goes via the former.

 * When pretty-printing a IfaceDecl for an algebraic data type, and
   doing so in Haskell-98 syntax, we were silently assuming that the
   universal type variables of the TyCon and the DataCon were the
   same. But that has not been true for some time. Result: a very
   confusing display.

   Solution: during the conversion to IfaceSyn, take the opportunity
   to make the universal type variables line up exactly.  This is very
   easy to do, makes the pretty-printing easy, and leaves open the future
   possiblity of not serialising the universal type variables of the
   data constructor.