Protocol changes in Wayland core introduced a new interface
wl_shell_surface, and moved all wl_shell surface methods into it. Adapt
the compositor and its Wayland backend, shell plugin, and all clients to
the new interface.
Depends on the Wayland core commit "protocol: introduce wl_shell_surface"
Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>