- Added new XCode projects for engine and all examples (ARC enabled, proper bundles etc.).
- Added external context manager with support for NSOGL.(this feature was available in ogl-es branch before).
- Removed *.nib dependencies from OSX project (menu is created programmatically).
- Added missing _IRR_OVERRIDE_ for some methods.
- Renamed MacOSX to OSX directories.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@5202 dfc29bdd-3216-0410-991c-e03cc46cb475