decode-events: counters for decode events errors

decode-events: counters for decode events errors

We want to add counters in order to track the number of times we hit a
decode event. A decode event is related to an error in the protocol
decoding over a certain packet.

This patch fist modifies the decode-event list, reordering it in order
to separate single packet events from stream-related events and adding
the prefix "decoder" to decode events.
The counters are created during the decode setup and the relative event
counter is increased every time a packet with the flag PKT_IS_INVALID is
finalized in the decode phase