ui/vnc: fix x offset calculation in vnc_refresh_server_surface

Signed-off-by: Peter Lieven <pl@kamp.de>
ui/vnc: vnc_dpy_copy fix 16 leftovers (2x)

Signed-off-by: Peter Lieven <pl@kamp.de>
ui/vnc: further simplify vnc_dpy_update

Signed-off-by: Peter Lieven <pl@kamp.de>
ui/vnc: fix off by one error in vnc_dpy_switch

Signed-off-by: Peter Lieven <pl@kamp.de>