This patch adds support for the CLASSIFY target which sets skb->priority.
Some qdiscs can use this value for classification, among these are

- atm
- cbq
- dsmark
- pfifo_fast
- htb
- prio

This target is only valid in the POST_ROUTING chain of the mangle table.

Usage:
	iptables -t mangle -A POSTROUTING .. -j CLASSIFY --set-class MAJOR:MINOR
