jez becomes jnz, complete cmp+jmp contraction

lisc/test/loop.ssa

@@ -8,7 +8,7 @@
 	%n  =w phi @start   0, @loop %n1
 	%n1 =w sub %n, 1
 	%s1 =w add %s, %n
-	jez %n1, @end, @loop
+	jnz %n1, @loop, @end
 
 @end
 	ret