swaynag: damage the cursor surface on update
swaynag: damage the cursor surface on update

When the cursor surface gets updated, it should be damaged.

This also bumps up `wl_compositor` to version 4 to be able to use
`wl_surface_damage_buffer`.

1ace/sway,SirCmpwn/sway,ascent12/sway,ascent12/sway,1ace/sway,1ace/sway,ascent12/sway