Log Message:
Add x11/modular-xorg-xwayland.

XWayland is a fully fledged X server implementation that acts as a proxy
between X11 clients and a Wayland compositor.

It runs as a specialized Wayland client, while optionally using a set of
XWayland specific Wayland protocols for implementing certain functionality.

The Wayland compositor acts both as the Wayland display server XWayland
connects to, as well as the window manager.