On a new set of laptops like the Lenovo T440 the trackstick does not have
physical buttons. Instead, the touchpad's top edge is supposed to acts
software button area. To avoid spurious cursor jumps when the trackstick is in
use and the finger is resting on the touchpad, add another mode that disables
motion events.

Enabled by syndaemon with -t click-only, the default stays unchanged. No
specific integration with the traditional disable-while-typing is needed. On
such touchpads, disabling motion events is sufficient to avoid spurious
events and we don't want to stop HW buttons to send events.

Note that this only adds the new state to the driver and to syndaemon, there
is nothing hooked up otherwise to actually monitor the trackstick.

Special note for syndaemon: optional arguments are a GNU extension, so work
around it by messing with an optstring starting with ":" which allows us to
manually parse the options.

Original version of this patch by John Pham <jhnphm@gmail.com>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>