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

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

Add support for virtual interfaces. These have no phy chip and, hence, we
need to handle interfaces without phy specially.

Add a program for configuration of the ATM drivers and the IP over ATM
stuff. This utility allows inspection of the ATM characteristics,
the PHY layer, including statistics of both, the retrival of the
list of currently open channels and also allows access to utopia(4).