Add dtrace SDT probe ipfw:::rule-matched.

It helps to reduce complexity with debugging of large ipfw rulesets.
Also define several constants and translators, that can by used by
dtrace scripts with this probe.

Reviewed by: gnn
Obtained from: Yandex LLC
MFC after: 2 weeks
Sponsored by: Yandex LLC
Differential Revision: https://reviews.freebsd.org/D26879