Don't interpret ABS_MT_TOUCH_MAJOR == 0 as touch release

On n8013 at least, this event is sometimes/often sent on touch start which
causes touches to be randomly rejected and throws you back to the start screen.

Touch releases still work fine for me, since it sends ABS_MT_TRACKING_ID == -1
for that purpose.

Adds a flag TW_IGNORE_MAJOR_AXIS_0 to configure this behavior.

Change-Id: I14bb036a2c2d4ee676b642c3ab297c55bb6c2084