Adds runtime for cocos2d-x v3.2

Copies v3.1
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
Updates README with v3.2 information
Merge pull request #256 from ricardoquesada/cocos2dx_v32

Cocos2dx v32