This allows one to force consistent printing of numeric port numbers like
we do with -n for other tools like netstat (just that -n was already taken)
rather than the service names.
-P is currently unused in OpenBSD so the change is eligible for upstreaming.
PR: misc/151015
Submitted by: Matt Koivisto (mkoivisto sandvine.com)
Sponsored by: Sandvine Incorporated
MFC after: 1 week