Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Regulatory fixups:
o add missing channel flags for ECM, indoor, and outdoor constraints
o use HT capabilities to short-circuit HT20/HT40 channel construction
o rewrite 1/2 and 1/4 width channel handling yet again; previously
we assumed there was a full-width version of the channel in the
calibration table but that's not always true (e.g. for the Public
Safety Band), now we first check the calibration table for the
exact channel we want then fall back to the heuristics we used before
o fix HT channel construction; wasn't adjusting band edges for HT40
channel bandwidth requirements

add support for max antenna gain (not used at the moment)

Improve regdomain.xml parser:
o store XML_Parser in the state block so we can report line numbers for errors
o complain about netband w/o mode
o complain about unknown modes
o complain about band w/o enclosing netband
o complain about duplicate freqband
o complain about unknown channel flags
o complain about band w/o freqband's
o complain about band w/o maxpower
o complain about country w/o ISO cc
o complain about country w/o regdomain reference

Multi-bss (aka vap) support for 802.11 devices.

Note this includes changes to all drivers and moves some device firmware
loading to use firmware(9) and a separate module (e.g. ral). Also there
no longer are separate wlan_scan* modules; this functionality is now
bundled into the wlan module.

Supported by: Hobnob and Marvell
Reviewed by: many
Obtained from: Atheros (some bits)