xserver-xorg/xwayland: 'Clarify' xserver license

xserver-xorg/xwayland: 'Clarify' xserver license

The Xserver license, https://gitlab.freedesktop.org/xorg/xserver/-/blob/main/COPYING
is a bit of a challenge to decode. Whilst overall thought to be MIT, there
are many other simlar/related licences included in there.

The make our license data more accurate, update to include all the license
variants present.

I have submitted a patch upstream to add identifiers to the COPYING file to
make it clearer where these come from and save others from repeating this painful
exercise:

https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2218

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>