GL_SGIX_async
http://oss.sgi.com/projects/ogl-sample/registry/SGIX/async.txt
	GL_ASYNC_MARKER_SGIX 0x8329
	void glAsyncMarkerSGIX (GLuint marker)
	void glDeleteAsyncMarkersSGIX (GLuint marker, GLsizei range)
	GLint glFinishAsyncSGIX (GLuint* markerp)
	GLuint glGenAsyncMarkersSGIX (GLsizei range)
	GLboolean glIsAsyncMarkerSGIX (GLuint marker)
	GLint glPollAsyncSGIX (GLuint* markerp)