GL_APPLE_fence
http://www.opengl.org/registry/specs/APPLE/fence.txt
GL_APPLE_fence
	GL_DRAW_PIXELS_APPLE 0x8A0A
	GL_FENCE_APPLE 0x8A0B
	void glDeleteFencesAPPLE (GLsizei n, const GLuint* fences)
	void glFinishFenceAPPLE (GLuint fence)
	void glFinishObjectAPPLE (GLenum object, GLint name)
	void glGenFencesAPPLE (GLsizei n, GLuint* fences)
	GLboolean glIsFenceAPPLE (GLuint fence)
	void glSetFenceAPPLE (GLuint fence)
	GLboolean glTestFenceAPPLE (GLuint fence)
	GLboolean glTestObjectAPPLE (GLenum object, GLuint name)