EZGCD _ _ _ _ _ _ _ _ _ _ _ _ switch

When ezgcd and gcd are on, greatest common divisors are computed using the EZ GCD algorithm that uses modular arithmetic (and is usually faster). Default is off.

As a side effect of the gcd calculation, the expressions involved are factored, though not the heavy-duty factoring of factorize. The EZ GCD algorithm was introduced in a paper by J. Moses and D.Y.Y. Yun in <Proceedings of the ACM>, 1973, pp. 159-166.

Note that the gcd switch must also be on for ezgcd to have effect.