WGL_NV_render_texture_rectangle
http://oss.sgi.com/projects/ogl-sample/registry/NV/render_texture_rectangle.txt
WGL_BIND_TO_TEXTURE_RECTANGLE_RGB_NV 0x20A0
WGL_BIND_TO_TEXTURE_RECTANGLE_RGBA_NV 0x20A1
WGL_TEXTURE_RECTANGLE_NV 0x20A2