[cocos2d] Some cleanup
[cocos2d] Fix the -define for chipmunk
[cocos2d] Use own CCVertex*

Stop depending on OpenTK structs, for compatibility between Xamarin.iOS
and Xamarin.Mac
[cocos2d] Mac: remove some preprocessor macro in favor of a sed command
[cocos2d] Fix the Is* properties for CCLayer
[cocos2d] CCLayer: split for ios/osx

CCLayer is so different tht it's better to have 2 different interfaces
instead fo a lot of #if.
Finally implement the CCAccelerometerDelegate
Also fix the interface which was not quite right for none of the
profiles
Merge pull request #116 from StephaneDelcroix/cocos2d

Cocos2d: various cleanups