"We see no reason why this rule, giving effect to disclaimer of claim scope during reexamination or reissue, should not also apply in the context of intervening rights.  In fact, a contrary rule would allow patentees to abuse the reexamination process by changing claims through argument rather than changing the language of the claims to preserve otherwise invalid claims and, at the same time, avoid creating intervening rights as to those claims.  Therefore, if the scope of the claims actually and substantively changed because of Marine Polymer’s arguments to the PTO, the claims have been amended by disavowal or estoppel, and intervening rights apply.  This is so even though Marine Polymer did not amend the language of its claims on reexamination."