Fix cursor visibility on surface commit

Created by: ixru

When spawning a new window in Rootston the cursor will disappear if it is over the surface. It is supposed to be set to a surface specific cursor. I think this is caused by the client sending an empty cursor surface when requested causing cursor->visible to be set to false. The surface is then committed but the visibility is not updated so it stays hidden until it registers movement.

I'm unsure if I put it in the correct place though. Maybe it should be called inside output_cursor_commit since it updates the dimenstions, I don't know what consequences that will have though.