o revamp IPv4+IPv6+bridge usage to match API changes
o remove pfil_head instances from protosw entries (no longer used)
o add locking
o bump FreeBSD version for 3rd party modules
Heavy lifting by: "Max Laier" <max@love2party.net>
Supported by: FreeBSD Foundation
Obtained from: NetBSD (bits of pfil.h and pfil.c)
not removing tabs before "__P((", and not outdenting continuation lines
to preserve non-KNF lining up of code with parentheses. Switch to KNF
formatting and/or rewrap the whole prototype in some cases.