This new protocol aims to let clients define the remaining bits of the color
encoding they are using in their buffers.

In particular, this lets clients define the how the alpha has been encoded and
how conversions from YCbCr to RGB take place.

Signed-off-by: Sebastian Wick <sebastian.wick@redhat.com>
Co-authored-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Co-authored-by: Robert Mader <robert.mader@collabora.com>
Co-authored-by: Sebastian Wick <sebastian.wick@redhat.com>
Co-authored-by: Simon Ser <contact@emersion.fr>
Co-authored-by: Xaver Hugl <xaver.hugl@kde.org>