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

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

This commit was generated by cvs2svn to compensate for changes in r129330,
which included commits to RCS files with non-trunk default branches.

This is smbmsg(8), a small utility to send/receive SMBus messages.

Also included is a `bus-probe' modus of operation to help scanning
an I2C bus.