Implemented numeric constants

examples/hello/hello.q

@@ -1,4 +1,8 @@
 main() {
-	syscall(1, 1, 4194305, 3)
-	syscall(60, 0)
+	let write = 1
+	let exit = 60
+	let stdout = 1
+
+	syscall(write, stdout, 4194305, 3)
+	syscall(exit, 0)
 }