GL_NV_copy_depth_to_color
http://www.opengl.org/registry/specs/gl/NV/copy_depth_to_color.txt
GL_NV_copy_depth_to_color
	GL_DEPTH_STENCIL_TO_RGBA_NV 0x886E
	GL_DEPTH_STENCIL_TO_BGRA_NV 0x886F