Reset num_active_touches on DeviceOff (#52496)
Reset num_active_touches on DeviceOff (#52496)

When disabling the device, reset num_active_touches to zero. Otherwise,
num_active_touches stays at the value it was on DeviceOff(). Future touches
add to that value until the index may go past priv->open_slots[].
That causes spurious memory corruption on touch ends.

And as of 55fc42e7c9b4948cadd4f98ef7b6a3b12e268e3e we ignore pre-existing
touches anyway.

Test-case:
- place num_touches fingers on the touchpad
- xinput disable <device>
- lift fingers
- xinput enable <device>
- place finger on device, num_active_touches is now (num_touches + 1)

X.Org Bug 52496 <http://bugs.freedesktop.org/show_bug.cgi?id=52496>

Signed-off-by: Peter Hutterer <b9c50af7afa7642f6f854434cda9ffe54ece8b85@who-t.net>
Reviewed-by: Chase Douglas <69e02ec421aa70a149511825d897f2549ceee9a2@canonical.com>

mad-s/xf86-input-synaptics-absolute,mad-s/xf86-input-synaptics-absolute