Allow PAD only interface without setting up EV_ABS and/or EV_X/Y

Wacom kernel driver has been merged to HID subsystem. As a bonus,
we also allow PAD to report its data on its own interface. To declare
the exact event types, we should not set EV_ABS or EV_X/Y for PADs
on most tablets.

However, xf86-input-wacom is not designed to handle this case. This
patch makes future PAD-only, or even expresskey-only, tablets work
properly.

Signed-off-by: Ping Cheng <pingc@wacom.com>
Remove hardcoded function name - usbProbeKeys

"in the future we should use __func__ instead of harcoding
function names." -- Peter Hutterer

Signed-off-by: Ping Cheng <pingc@wacom.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Ensure input device fd gets closed after use

Fixes a minor error in commit 52fe01c which results in the driver
invalidating an fd prior to (potentially) closing it. This reversed
order causes us to leak the fd and can result in eventual exhasution.

Fixes SF #263

Signed-off-by: Jason Gerecke <killertofu@gmail.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Allow xsetwacom to recognize 'insert' as a key

Signed-off-by: Jason Gerecke <killertofu@gmail.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
xsetwacom: Warn if keycode could not be found

As described at SF #267, xsetwacom provides no indication if a valid
keysym has no keycode in the current keyboard layout. This provides
such a warning and updates language of a preceeding warning to be
more accurate.

Signed-off-by: Jason Gerecke <killertofu@gmail.com>