Update xdg-shell.xml
wayland-surface: Fill in the maximized/fullscreen hints to the configure event
wayland-surface: Allow extension resources to be double-destroyed

As they will be on shutdown... I'm not sure if this is a wayland-server
bug or not, but we should guard against it anyway.
window-actor: Don't set ourselves as reactive twice
window-actor: Set as unreactive when hiding

This means that we should never pick the actor when it's being destroyed.
pointer: Remove dead and incorrect code

Now that we can never pick a destroying actor, we can remove these
bad asserts.