For the puck/lens cursor tool we need to artificially reduce proximity
detection. These tools are usually used in a relative mode (i.e. like a mouse)
and thus require lifting and resetting the tool multiple times to move across
the screen. The tablets' distance detection goes too far, requiring the user
to lift the device several cm on every move. This is uncomfortable.

Introduce an artificial distance threshold for the devices with the default
value taken from the X.Org wacom driver. If a tool is in proximity but outside
of this range, fake proximity events accordingly.

If a button was pressed while we were out of range we discard that event and
send it later when we enter proximity again.

This is the simple implementation that only takes one proximity out value (the
one from the wacom driver) and applies it to all. Those devices that support a
button/lens tool and have a different default threshold are well out of date.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>

[rebased, tests updated for new axis percentage behavior (8d76734f

)]

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>