surprisingly, a duplicate case can cause 5c to loop generating
instructions until memory runs out. better to stop cc/pswt.c once
the case is known to be wrong.
it doesn't cause 8c to fail because it doesn't do the direct case
the same way
		while(q->val != v) {
			nextpc();
			p->as = ABCASE;
			patch(p, def);
			v++;
		}
and the subsequent v++ for the next case doesn't expect a matching pair of q->val.