modified:   mahjong/game.h
	new file:   mahjong/ai.hpp
ai has been embedded into NPC and game.

but the real algorithm has not been implemented yet.
	modified:   mahjong/ai.hpp
	modified:   mahjong/game.cpp
	modified:   mahjong/game.h
	modified:   mahjong/player.hpp
clear
	modified:   mahjong/player.hpp