GL_ARB_texture_rectangle
http://oss.sgi.com/projects/ogl-sample/registry/ARB/texture_rectangle.txt
	GL_TEXTURE_RECTANGLE_ARB 0x84F5
	GL_TEXTURE_BINDING_RECTANGLE_ARB 0x84F6
	GL_PROXY_TEXTURE_RECTANGLE_ARB 0x84F7
	GL_MAX_RECTANGLE_TEXTURE_SIZE_ARB 0x84F8
	GL_SAMPLER_2D_RECT_ARB 0x8B63
	GL_SAMPLER_2D_RECT_SHADOW_ARB 0x8B64