o Handle the 'up/down' buttons some touchpads have as
a z-axis (scrollwheel) as recommended by the specs
o Report the buttons as button4 and button5 instead
of button2 and button4, button2 can be emulated by
pressing button1 and button3 simultaneously. This
allows one to use the two extra buttons for other
purposes if one so desires.
Tested by: many subscribers to -current
Approved by: njl