Losing the precision resulted in wlr_cursor and wlr_seat::pointer_state
getting out of sync during pointer motion in seatop_down.
Since the difference was always under 1 px, it was practically
impossible to notice in normal use.
But because of being out of sync, cursor_rebase would always end up
incorrectly calling wlr_seat_pointer_notify_motion from
seatop_default_begin (on releasing mouse button) which broke cursor
locking.
See #5405Closes#4632
d0fe721fbb