If the pointer is warped the position change should be treated like
a change coming from the input device. Our normal processing should
take place.
A problem in this case is the timestamp to pass to the wayland server.
Normally our timestamps come from the backend/libinput and we don't
know the next one. As an intermediate solution we just use the last
timestamp on the seat. In future a solution could be to not use the
backend's timestamp at all, but have our own timestamp handling.
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