Build file modifications add support for OSX 10.8 gameplay builds.
Adds Quartz, OpenAL, OpenGL and IOKit frameworks.
Only uses gameplay external dependencies to relevant to OSX.
Compiles 32-bit by default and uses c++0x standard.

Notes:
1. Gameplay3d and hx-gameplay builds must have matching '-fvisibility'
	flag settings. The Gameplay project file doesn't set it. hxcpp
	sets -fvisibility=hidden.
2. Must run the build command with the '-DHXCPP_CLANG' in order to use
	clang (Should be set as the default in the future).