GL_EXT_texture_compression_latc
http://developer.download.nvidia.com/opengl/specs/GL_EXT_texture_compression_latc.txt
	GL_COMPRESSED_LUMINANCE_LATC1_EXT 0x8C70
	GL_COMPRESSED_SIGNED_LUMINANCE_LATC1_EXT 0x8C71
	GL_COMPRESSED_LUMINANCE_ALPHA_LATC2_EXT 0x8C72
	GL_COMPRESSED_SIGNED_LUMINANCE_ALPHA_LATC2_EXT 0x8C73
