[RFC] Drop DMX DDX

[Povilas Kanapickas]

Hello,

It turns out xdmx currently crashes when any client attempts to use GL
and it has been in such state for about 14 years. There was a patch to
fix the problem [1] 4 years ago, but it never got merged. The last
activity on any bugs referring to xdmx has been more than 4 years ago.

Given such situation, I find it unlikely that anyone is still using xdmx
and just having the code is a drain of resources.

Therefore I propose to drop xdmx not only from master branch, but also
from X server 21.1. I think this is good enough reason to delay the RC1
of X server 21.1 by some more time.

There is a merge request [2] with the changes needed to make this
happen. I would like to ask to continue discussions there so that they
are kept in a single place.

Regards,
Povilas

[1]: https://lists.x.org/archives/xorg-devel/2017-June/053919.html
[2]: https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/743