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

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

Add ibcntl as alias for ibcnt
Add ibsta and start to use it.
Rename the argument structure more sensibly.
Improve timeout and error handling

Further elaborate the GPIB driver. We now support a minimal subset of
the ibfoo() API.