GL_EXT_debug_marker
http://www.khronos.org/registry/gles/extensions/EXT/EXT_debug_marker.txt
GL_EXT_debug_marker
	void glInsertEventMarkerEXT (GLsizei length, const GLchar* marker)
	void glPushGroupMarkerEXT (GLsizei length, const GLchar* marker)
	void glPopGroupMarkerEXT (void)
