obsolete instance protocol and class-slots

obsolete instance protocol and class-slots

  UPDATE-INSTANCE-FOR-REDEFINED-CLASS needs to be called when
  the set of class-slots changes.

  ...we /tried/ to do that, but embarrasingly

   (LOOP FOR X IN LIST1
         FOR Y IN LIST2
         ALWAYS ...)

  returns T if either list has elements missing from the other in the
  tail as the iteration terminates when list runs out. Oops.