EvdevTouch: Don't remove released touch data for Type B; only ignore slot

The Type B protocol states that touch slots with an ID of -1 should be
considered unused, but data should be retained if that slot becomes
active again later. Instead of removing the contact from the contact list,
only "disable" it. This contact can later be reused if the slot becomes
active again.
Merge pull request #26 from xknight/touch

EvdevTouch: Don't remove released touch data for Type B; only ignore slot