Added more tests, function calls work

Fixed a bunch of bugs in other opcodes, too

test/sample2.5.c0

@@ -0,0 +1,7 @@
+int main () {
+	int i; int sum = 0;
+	for (i = 15; i <= 122; i++)
+		sum += i;
+	assert(sum == 0);
+	return sum;
+}