HEADS UP: new wlan code

I've committed the changes to switch the 802.11 support over to the code in 
sys/net80211.  The new code is significantly different as it has been 
revamped to support multi-mode devices, add fine-grained locking, and 
support more of the 802.11 protocol.  Drivers that depend on the code have 
been changed (e.g. wi).  Drivers and programs that included 
<net/if_ieee80211.h> have been changed to the new scheme.  Ideally you 
should see no regressions but beware of changes to the wi driver.  Please 
report any new problems to me (not Warner).

As a byproduct of these changes you can now use the Atheros driver w/o 
patching the tree.  man ath(4) for info on the driver.

	Sam