Wayland server side decoration

[Jjagg]

There's been a lot of discussion on this topic. Looks like Wayland is getting a server side decoration protocol after all named xdg-decoration. Though it will probably not be supported by all compositors. GNOME discussion: https://gitlab.gnome.org/GNOME/mutter/issues/217
SDL discussion: https://bugzilla.libsdl.org/show_bug.cgi?id=2710

It should be documented that a Wayland compositor might not support decorations. I'm not a fan of implementing a fallback client-side decoration, it adds tons of complexity.

• xdg-decoration support (server side decoration) -> 0f2af1d
• server-side decoration enable/disable resize (?)
• client-side decoration fallback
• client-side decoration resize/move