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

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

Update iwn(4) firmware blobs:
- bump iwn1000fw to 39.31.5.1
- bump iwn5000fw to 8.83.5.1
- bump iwn6050fw to 41.28.5.1

iwn(4) update. Notable changes:
* new firmware
* untested support for 1000 and 6000 series
* bgscan support
* remove unnecessary RXON changes
* allow setting of country/regdomain by enforcing channel flags read
from the EEPROM
* suspend/resume fixes
* RF kill switch fixes
* LED adjustments
* several bus_dma*() related fixes
* addressed some LORs
* many other bug fixes

Submitted by: Bernhard Schmidt <bschmidt at techwires.net>
Obtained from: Brandon Gooch <jamesbrandongooch at gmail dot com> (LED
related changes), Benjamin Kaduk <kaduk at mit dot edu>
(LOR fixes), OpenBSD

Updates to the iwn driver:
* iwnfw has now been split into individual modules so autoloading of
firmware module(s) does work again.
* Changes have been made to RUN -> AUTH transition, this should fix the
issue reported by Glen and others.
* Brandon reported issues in iwn_cmd() with large commands, those have
been fixed to.
* DEAUTH is now handled correctly.

Submitted by: Bernhard Schmidt <bschmidt at techwires.net>