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)

- Convert sc_sessions_mtx mutex to a rwlock, so in the fast path
(glxsb_process()) we don't block others when looking for our session.
- Simplify the loop responsible for freeing sessions on detach.
- No need to drop a lock around malloc(M_NOWAIT).
- Treat ses_used as boolean.
- Avoid gotos where possible.
- Various style(9) fixes.

Reviewed by: philip, Patrick Lamaiziere <patfbsd@davenulle.org>

Add glxsb(4) driver for the Security Block in AMD Geode LX processors (as
found in Soekris hardware, for instance). The hardware supports acceleration
of AES-128-CBC accessible through crypto(4) and supplies entropy to random(4).

TODO:

o Implement rndtest(4) support
o Performance enhancements

Submitted by: Patrick Lamaizière <patfbsd -at- davenulle.org>
Reviewed by: jhb, sam
MFC after: 1 week