input: Schedule pointer sprite repaint when cursor is set

input: Schedule pointer sprite repaint when cursor is set

If a cursor was set with wl_pointer.set_cursor but not in combination
with an action that has the side effect of damaging the region where the
cursor is positioned, it would not be drawn. This patch explicitly
schedules a repaint of the pointer sprite when it is set.

clickdot is updated to illustrate the bug; when moving the pointer over
clickdot, the pointer is hidden. When not having moved the pointer for
500 ms it is made visible using wl_pointer.set_pointer.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>