pf: Update to OpenBSD 4.2

pf: Update to OpenBSD 4.2

	All sorts of informations is now stored directly in
	the mbuf header instead of a seperate mbuf tag. This
	brings in a 100% performance increase in comparison
	to OpenBSD 4.1. For DragonFly this basically means
	this is the same performance as in 2.6, but we are
	equal again with OpenBSD's pf data structures.

	Necesary additions:

	sys/net: add more interface groups related functions

		if_creategroup()
		if_addgroup()
		if_delgroup()
		if_getgroup()
		if_getgroupmembers()

		Imported from OpenBSD

	carp: add carp_group_demote_adj()

	altq: re-add check of packet tagging

	fairq & red support, UDP nat'ing, reassembly fixed by Matthew Dillon