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

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

Support for the XScale PXA255 SoC as found on the Gumstix Basix and Connex
boards. This is enough to net-boot to multiuser.

Also supported is the SMSC LAN91C111 parts used on the netCF, netDUO and netMMC
add-on boards.

I'll be putting some instructions on how to boot this on the Gumstix boards
online soon.

This is still fairly rough and will be refined over time but I felt it was
better to get this out there where other people can help out.