说明：  模拟十字路口交通灯,实现红黄绿三灯闪烁，运用了延迟，不涉及定时器的使用，中断也没涉及，需要的可以了解。
(Simulation intersection traffic lights, red, yellow and green three lights flashing, the use of delay, not involved in the use of timer, interrupt is not involved, you can understand the need.)