Add more tests.

remove unnecessary pkg.

It can be resurrected by reverting this commit.

It can be resurrected by reverting this commit,
if XCVB is ever resurrected (which is unlikely).

It was never fully completed, probably will never be, and can be restarted
by reverting this commit if needs be.

If someone wants to try, I recommend using IOlib as a portable backend.

They were so far unsuccessful experiments.
Better replace them by an iolib backend.

return what it returns when CALL-FUNCTION'ed with the condition,
except for NIL (continue) and T (signal error).

It's more general, but it's also SLIGHTLY INCOMPATIBLE,
depending on values provided. So BEWARE!

Update copyright dates.

Add missing declare ignore.

Have RUN/NIL for the no-output variant, RUN/INTERACTIVE for the interactive variant.