This change introduces a package that provides basic functions for the
manipulation of logical network interfaces, interface addresses and
data links on Solaris.

As BSD variants implement routing socket and routing messages, Linux
implements netlink socket and netlink messages, Solaris implements
STREAMS-like interface for reading, writing network facility
information inside the kernel. The package wraps various I/O control
calls which involve message exchanges between kernel protocol modules
in exposed APIs.

At present, the package supports Solaris 11 or above.

Updates golang/go#7177.

Change-Id: I192d85e53b0bee942dfefca0f73a3eb94ab8bfe9
Reviewed-on: https://go-review.googlesource.com/29893Reviewed-by: Ian Lance Taylor <iant@golang.org>