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 device driver support for the Level 1 LXT1001 NetCellerator
gigabit ethernet controller chip. This device is used on some
fiber optic gigE cards from SMC, D-Link and Addtron. Jumbograms and
TCP/IP checksum offload on receive are supported. Hardware VLAN
filtering is not, because it doesn't play well with our existing
VLAN code. Also add manual page.

There is a 4.x version of this driver available at
http://www.freebsd.org/~wpaul/Level1/4.x if anyone feels adventurous
and wants to test it. I still need to do performance testing and
tuning with this device.

(For my next trick, I will make the 3Com 3cR990 sit up and beg.)