Dear all,

a CLASS entity cannot have the PARAMETER attribute.
This is detected in some situations, but in others
we ICE because we never reach the existing check.
Adding a similar check when handling the declaration
improves error recovery.

The initial patch is by Steve.  I adjusted and moved
it slightly so that it also handles CLASS(*)
(unlimited polymorphic) at the same time.

Regtested on x86_64-pc-linux-gnu.  OK for mainline?

This patch actually addresses multiple PRs, some of
which are marked as regressions.  As I consider the
patch safe, I would like to backport to open branches
as far as it seems appropriate.

Thanks,
Harald