1.0.2.14: Speed up constraint propagation

1.0.2.14: Speed up constraint propagation

        * Rewrite ADD-EQL-VAR-VAR-CONSTRAINT to do a constant number of
          passes over the constraint set, rather than an amount proportional
          to the amount of EQL constraints on the variables in question.
        * Use SSET-MEMBER directly in CONSTRAIN-REF-TYPE, rather than
          a COPY-SSET and SSET-INTERSECTION.