CFT: major wireless changes

This patch against HEAD imports the work that's been sitting in the 
sam_wifi p4 branch:

http://people.freebsd.org/~sam/sam_wifi-20070601.patch.gz

To apply it do something like

cd /usr/src
gzcat sam_wifi-20070601.patch.gz | patch -p4

Expect one reject in sys/net80211/ieee80211_input.c.rej; it can be ignored.

These changes do the following:

o significantly change net80211 data structures in ways required by the 
multi-bss/vap support and for 802.11n
o overhaul scanning to support background scanning and roaming
o add basic 802.11n support (drivers coming separately)
o add support for Atheros' protocol extensions (e.g. fast frames)
o purge compatibility ioctls in net80211 for wicontrol et. al.
o add experimental radiotap additions for handling 802.11n packets
o update ifconfig

Note that scanning in net80211 has been broken out into separate modules 
and you must now add device lines for wlan_scan_ap+wlan_scan_sta (as 
appropriate) or load the modules as you do the crypto modules.

These changes have been extensively tested in one form or another for 
several years but the current code may have some minor issues.  Some 
drivers have been tested more than others.  In particular iwi just 
recently got some work and it appears to need some more fixups to deal 
with "stuck scan" and beacon miss issues.

This is the work of many people including Kip Macy, Max Laier, Sephe 
Ziehau, Andrew Thompson, and Kevin Lo.  Please report problems to this list.

	Sam