Wayland support

This issue tracks what is needed to port Wayland to Redox.

The main difference between X11 and Wayland is the architecture and communication, in X11 you have a display server, window manager and application clients, while in Wayland the display server and window manager clients are one program (the compositor), each Wayland compositor has the freedom to implement its rendering logic and input interfaces.

(In both display servers the user programs are clients)

TODOs

• Implement the necessary Unix domain socket features #1595
• Support for passing memfd or POSIX shared memory fd's (shm_open) over the socket
• Support for signalfd
• Support for timerfd
• Port libwayland
• Port and test the smallvil and anvil example compositors from Smithay
• Port the COSMIC compositor (Jeremy is doing that)

COSMIC Desktop Rendering Strategy

As Redox don't have GPU drivers yet we need to use software rendering (AKA CPU rendering) in our GUI (Orbital does)

The COSMIC Desktop team aims to implement software rendering on the COSMIC compositor, thus we just need to use this rendering backend and port the other interfaces.