When a record contruction or pattern uses a data constructor
that isn't in scope, we may produce spurious ambiguous-field
errors (Trac #14307).  E.g.

   f (A { fld = x }) = e

where 'A' is not in scope.  We want to draw attention to the
out-of-scope data constructor first; once that is fixed we
can think about the fields.

This patch suppresses the field errors if the data con is out
of scope.