GL_EXT_texture_sRGB_decode
https://www.khronos.org/registry/OpenGL/extensions/EXT/EXT_texture_sRGB_decode.txt
GL_TEXTURE_SRGB_DECODE_EXT 0x8A48
GL_DECODE_EXT 0x8A49
GL_SKIP_DECODE_EXT 0x8A4A