cocos2dx: CCScheduler

Add a function name as "performTaskInCocosThread".
calls a function on the cocos2d thread.
Useful when you need to call a cocos2d function from another thread.
Note that return value indicate function running state in cocos2d thread.
This function is thread safe.

Signed-off-by: tangzhenqiang <tangzhenqiang@letv.com>