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

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

Parse "getifname" using the standard parse string type.

Fixed an off-by-one error when dealing with interface name
(if_xname is NUL-terminated).

Don't waste time making a copy of if_xname in constructor.

/* -> /*- for license, minor formatting changes

sppp (4) to netgraph (4) node. As always: I'l connect it to the
system after extra check.

Approved by: imp (mentor)
Approved by: julian (in general)