The X server swapping code is a huge attack surface, much of this code
is untested and prone to security issues. The use-case of byte-swapped
clients is very niche, so let's disable this by default and allow it
only when the respective config option or commandline flag is given.
For Xorg, this adds the ServerFlag "AllowByteSwappedClients" "on".
For all DDX, this adds the commandline options +byteswappedclients and
-byteswappedclients to enable or disable, respectively.
Fixes#1201https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1029
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>