Avoid misbehavior in foreign key checks when casting to a datatype for which

Avoid misbehavior in foreign key checks when casting to a datatype for which
the parser supplies a default typmod that can result in data loss (ie,
truncation).  Currently that appears to be only CHARACTER and BIT.
We can avoid the problem by specifying the type's internal name instead
of using SQL-spec syntax.  Since the queries generated here are only used
internally, there's no need to worry about portability.  This problem is
new in 8.3; before we just let the parser do whatever it wanted to resolve
the operator, but 8.3 is trying to be sure that the semantics of FK checks
are consistent.  Per report from Harald Fuchs.