Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

purge dead code

fix big-endian machines

Fix monitor mode vaps to work as intended:
o track # bpf taps on monitor mode vaps instead of # monitor mode vaps
o spam monitor mode taps on tx/rx
o fix ieee80211_radiotap_rx_all to dispatch frames only if the vap is up
o while here print radiotap (and superg) state in show com

Fix handling of devices w/o radiotap support:
o do not attach DLT_IEEE802_11_RADIO unless both tx and rx headers are
present; this is assumed in the capture code paths
o verify the above with asserts in ieee80211_radiotap_{rx,tx}
o add missing checks for active taps before calling ieee80211_radiotap_rx

Overhaul monitor mode handling:
o replace DLT_IEEE802_11 support in net80211 with DLT_IEEE802_11_RADIO
and remove explicit bpf support from wireless drivers; drivers now
use ieee80211_radiotap_attach to setup shared data structures that
hold the radiotap header for each packet tx/rx
o remove rx timestamp from the rx path; it was used only by the tdma support
for debugging and was mostly useless due to it being 32-bits and mostly
unavailable
o track DLT_IEEE80211_RADIO bpf attachments and maintain per-vap and
per-com state when there are active taps
o track the number of monitor mode vaps
o use bpf tap and monitor mode vap state to decide when to collect radiotap
state and dispatch frames; drivers no longer explicitly directly check
bpf state or use bpf calls to tap frames
o handle radiotap state updates on channel change in net80211; drivers
should not do this (unless they bypass net80211 which is almost always
a mistake)
o update various drivers to be more consistent/correct in handling radiotap
o update ral to include TSF in radiotap'd frames
o add promisc mode callback to wi

Reviewed by: cbzimmer, rpaulo, thompsa