GL_EXT_texture_sRGB_decode
http://www.opengl.org/registry/specs/gl/EXT/texture_sRGB_decode.txt
GL_EXT_texture_sRGB_decode
	GL_TEXTURE_SRGB_DECODE_EXT 0x8A48
	GL_DECODE_EXT 0x8A49
	GL_SKIP_DECODE_EXT 0x8A4A