Repair bug reported by Huxton, 1/24/01. We need to include a rule's

original table ('OLD' table) in its join tree if OLD is referenced by
either the rule action, the rule qual, or the original query qual that
will be added to the rule action.  However, we only want one instance
of the original table to be included; so beware of the possibility that
the rule action already has a jointree entry for OLD.