Cocos2dx v32

Supports cocos2d-x v3.2

* Changes `draw()` with the new v3.2 API: `bool transformUpdated` -> `uint32_t transformFlags`
* cocos2d-ified the API:
    * `const char*` -> `const std::string&`
    * constructors and destructors are `protected` (not `public`)
    * using `_` prefix for ivars
Any reason to make all fields protected?