Made HeyBox2D work with Marmalade 7

HeyBox2D was written for sub-pixel rendering based on the legacy
implementation of GX.
Upgraded to Box2D 2.3.0

The Box2D code is in original state. The release build in XCode issues
warnings.

The HeyBox2D sample project has been updated:
- the b2World constructor no longer has 2 arguments
- the b2LoopShape has been replaced with the b2ChainShape
Merge pull request #1 from olilanz/master

Made HeyBox2D work with Marmalade 6 and 7
Upgraded Box2D to version 2.3.0