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

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

Committed the xbox syscons(8)-able console driver.

Reviewed by: arch@ (no comments)
Approved by: imp (mentor)

Cleaned the memory initialization up, moved some defines from the framebuffer
to an include file.

Reviewed by: imp
Approved by: imp (mentor)

Add support for XBOX to the FreeBSD port. The xbox architecture is
nearly identical to wintel/ia32, with a couple of tweaks. Since it is
so similar to ia32, it is optionally added to a i386 kernel. This
port is preliminary, but seems to work well. Further improvements
will improve the interaction with syscons(4), port Linux nforce driver
and future versions of the xbox.

This supports the 64MB and 128MB boxes. You'll need the most recent
CVS version of Cromwell (the Linux BIOS for the XBOX) to boot.

Rink will be maintaining this port, and is interested in feedback.
He's setup a website http://xbox-bsd.nl to report the latest
developments.

Any silly mistakes are my fault.

Submitted by: Rink P.W. Springer rink at stack dot nl and
Ed Schouten ed at fxq dot nl