Wayland backend update

[Ladislav Michl]

Hi there,

this is quick wayland backend update based on
https://github.com/ivucica/libs-back/tree/ivucica-wayland

Note that original Sergio's patch is rebased to current master,
the rest is just to make things work somehow again. You can find
current work in progress here:
https://paste.debian.net/1124403
https://paste.debian.net/1124404
https://paste.debian.net/1124405
https://paste.debian.net/1124406
https://paste.debian.net/1124407

..and a picture: https://ibb.co/DRFmH2T (so you can see there's work left)

This is just to have something to play with again. As I've never touched
Wayland nor GNUstep before and another winter holidays are about a year
in the future do not expect miracles. I can make some more cleanups
and perhaps prepare it for merge, but let's see how many people are
actually interested - Debian paste expires in 90 days ;-)

Happy New Year,
        ladis