一、cocos2d有段注释：* Passing two numbers (x,y) is much efficient than passing CCPoint object.
* This method is binded to lua and javascript.* Passing a number is 10 times faster than passing a object from lua to c++
意思是指：传送number型的值比传送CCPoint对象更有效率；特别是在lua和c++之间的传值；
