Add support for computed gotos

This is a GCC extension that allows C to use fast jump tables.

test/val/computedgoto.c

@@ -0,0 +1,55 @@
+static unsigned char val, val2;
+
+static void act(const unsigned char op) {
+
+	static const void * const arr[] = {
+		&&op0,
+		&&op1,
+		&&op2,
+		&&op3,
+		&&op4,
+		&&op5,
+		&&op6,
+	};
+
+	goto *arr[op];
+
+	op0:
+	val += 1;
+	return;
+
+	op1:
+	val += 2;
+	return;
+
+	op2:
+	val += 3;
+	return;
+
+	op3:
+	val2 += 1;
+	return;
+
+	op4:
+	val2 += 5;
+	return;
+
+	op5:
+	val2 += 7;
+	return;
+
+	op6:
+	val2 += 9;
+	return;
+}
+
+int main() {
+
+	val = val2 = 0;
+
+	act(1);
+	act(3);
+	act(5);
+
+	return val == 2 && val2 == 8 ? 0 : 1;
+}