@winipcfg 

I updated this PR, and used enum class for event type and listener type.
Could you check that here https://github.com/dumganhar/cocos2d-x/commit/d3afa5028979e3228b20c53b35b2282b6965b1a5 ?

I also added another variable called `EventListener::ListenerID _listenerID` for the key of `std::unordered_map`.

What do you think this change?