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

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

A diagnostic tool to go along with the vxge(4) 10GbE driver.
This tool can be used to print statistics, registers, and
other device specific information once the driver is loaded
into the kernel.

Submitted by: Sriram Rapuru from Exar
MFC after: 2 weeks