For an easier review process, this is a two-step change process,
in which pcap_cnt is first accessed by functions-to-be, implemented
as simple macros.
In the follow-up commit, the actual refactor is implemented with the new
function. The old macros are deleted.
Ticket: 7835
This can happen when the flow is UDP, but an ICMP unreachable is
returned, which gets assigned to the same flow.
Reference: https://github.com/ntop/nDPI/issues/2762
Split DetectHelperKeywordRegister into 2 functions, one for acquiring
a new keyword ID, and another to perform the registration.
This makes it easier to do the traditional C keyword initialization
with a dynamic ID.