Added the AI,but it need change
	modified:   Game2DExercise/WinMain.h
	modified:   Game2DExercise/bg.bmp
	new file:   Game2DExercise/bird.bmp
	modified:   Game2DExercise/girl0.bmp
	modified:   Game2DExercise/girl1.bmp
	modified:   Game2DExercise/girl2.bmp
	modified:   Game2DExercise/girl3.bmp
	modified:   Game2DExercise/main.cpp