[Cake] Backporting 'tc class' support

[Dave Taht]

I am curious if the new tc class support would allow for recognizing
sebastian's desire to have the llc (?) dsl control packets moved to
the higher priority tin?

Similarly, there were other things in early-sqm (like deprioritizing
ping, prioritizing dns) that I liked, but disliked using iptables to
use.

lastly, the hopelessly overloaded skb->priority field is hopefully
still not recognized for anything that actually sets skb->priority
naively?