PS/2 interface: sense multifinger taps on FingerHigh (#21427)
PS/2 interface: sense multifinger taps on FingerHigh (#21427)

Previously multifinger taps were sensed on the Z value > 0: this isn't
very correct.  Accorging to the specification, Z values below 30
correspond only to a very light taps or just floating fingers.  I had
run into the situation when I was clicking on the physical left button
and that click was transformed to the right button click via
ClickFinger2, but I wasn't tapping the touchpad at all.  Investigations
showed very small values of Z -- my other fingers were just floating
above touchpad.

This change also makes click (and finger) detection more consistent,
because it uses FingerHigh to detect taps everywhere.

X.Org Bug 21427 <http://bugs.freedesktop.org/show_bug.cgi?id=21427>

Signed-off-by: Eygene Ryabinkin <6ed1094f5ee8dcb87d917057819372ebd839b68b@codelabs.ru>
Signed-off-by: Peter Hutterer <b9c50af7afa7642f6f854434cda9ffe54ece8b85@who-t.net>
Acked-by: Henrik Rydberg <b7088a9c70345a9ab94cacab3cc3888d0a7dc884@euromail.se>
(cherry picked from commit ef2221322e62b94a88a8358e6513a3f6f232a28f)

RsrchBoy/xserver-xorg-input-synaptics,philipn/xserver-xorg-input-synaptics,RsrchBoy/xserver-xorg-input-synaptics,philipn/xserver-xorg-input-synaptics,philipn/xserver-xorg-input-synaptics