added METHOD_CASES, resolveq_cases_tac;
removed multi_resolveq;
improved 'tactic' method: bind thm(s) function;
GCD = WF_Rel +
consts gcd :: "nat*nat => nat"
recdef gcd "measure ((%(m,n).n))"
simpset "simpset() addsimps [mod_less_divisor]"
"gcd (m, n) = (if n=0 then m else gcd(n, m mod n))"
end