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

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

Add options GEOM_PART_GPT and options MSDOSFS to the DIR-825

Reviewed by: adrian@

Back out r253779 & r253786.

device if_bridge gets me a bridge device

Decouple yarrow from random(4) device.

* Make Yarrow an optional kernel component -- enabled by "YARROW_RNG" option.
The files sha2.c, hash.c, randomdev_soft.c and yarrow.c comprise yarrow.

* random(4) device doesn't really depend on rijndael-*. Yarrow, however, does.

* Add random_adaptors.[ch] which is basically a store of random_adaptor's.
random_adaptor is basically an adapter that plugs in to random(4).
random_adaptor can only be plugged in to random(4) very early in bootup.
Unplugging random_adaptor from random(4) is not supported, and is probably a
bad idea anyway, due to potential loss of entropy pools.
We currently have 3 random_adaptors:
+ yarrow
+ rdrand (ivy.c)
+ nehemeiah

* Remove platform dependent logic from probe.c, and move it into
corresponding registration routines of each random_adaptor provider.
probe.c doesn't do anything other than picking a specific random_adaptor
from a list of registered ones.

* If the kernel doesn't have any random_adaptor adapters present then the
creation of /dev/random is postponed until next random_adaptor is kldload'ed.

* Fix randomdev_soft.c to refer to its own random_adaptor, instead of a
system wide one.

Submitted by: arthurmesh@gmail.com, obrien
Obtained from: Juniper Networks
Reviewed by: obrien

This is an initial board configuration for the D-Link DIR-825 dual-band
802.11n router.

The flash layout defaults to a 1 MiB section for the kernel so I'm trying
very hard to squeeze a minimialistic (LZMA compressde) kernel image into
that.

I've verified that it boots through to single user mode fine.

Issues:

* USB doesn't yet work as a module - I need to add something else to the
USB AR71xx build before that will work.
* There's no switch PHY support - but for now it quite happily behaves
as a useful dumb switch out of the box. Phew.
* Since a previous flash attempt trashed my radio configuration block,
I haven't yet verified whether the wireless works correctly.
I'll test that out shortly (read: once I re-calibrate the board somehow.)

Thanks to ray@ and the zrouter project for doing some of the initial
hard work in figuring out how to bring this board up.