...net80211 function that will assign sequence numbers to
frames (which I haven't yet completely vetted!)
- teach ath(4) about using this new function to fill out sequence numbers for frames as appropriate.
- ath(4) - STA mode only; not IBSS or hostap modes yet!
- Go look at whether cabq frames should have sequence numbers allocated /after/ the beacon frame sequence numbers, for non-QoS data frames.