Cancel touch events when a low-level touch gesture occurs.

When the touch firmware or driver sends a key event that is triggered
by a low-level gesture such as a palm slap.  For this to work, the
touch device's .kl file must specify the "GESTURE" flag for each
key that is produced by a gesture.

Note that the "VIRTUAL" flag should also be specified for any such
keys for which we would like to generate haptic feedback.

eg. key 142   SLEEP   VIRTUAL GESTURE

Bug: 19264992
Change-Id: Ief494ec7e3ca66d2358a1001fdfae4f263ee1cd1