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

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

Remove bridge(4) from the tree. if_bridge(4) is a full functional
replacement and has additional features which make it superior.

Discussed on: -arch
Reviewed by: thompsa
X-MFC-after: never (RELENG_6 as transition period)

Add a device driver for the Broadcom BCM4401 ethernet controller,
written by Stuart Walsh and Duncan Barclay (with some kibbitzing by
me). I'm checking it in on Stuart's behalf.

The BCM4401 is built into several x86 laptop and desktop systems. For the
moment, I have only enabled it in the x86 kernel config because although
it's a PCI device, I haven't heard of any standalone NICs that use it. If
somebody knows of one, we can easily add it to the other arches.

This driver uses register/structure data gleaned from the Linux
driver released by Broadcom, but does not contain any of the code
from the Linux driver itself. It uses busdma.