garbage collect unused capabilities and configurations flags.

garbage collect unused capabilities and configurations flags.
add two capabilities flags: IEEE80211_C_HT for HT STAs (802.11n)
and IEEE80211_C_APPMGT which indicates the capability for an AP
to buffer unicast and multicast traffic for STAs in PS mode.
all drivers claiming HostAP support should support that but the
truth is that none of them do.
most of them are still at the 802.11b-only era and do not update
dynamic parts of beacons or process frames from ic_pwrsaveq.