lib: bring in sys/queue.h from FreeBSD tree

lib: bring in sys/queue.h from FreeBSD tree

Bring in sys/queue.h from the FreeBSD tree as lib/queue.h.

This header implements lists of various flavors using inline
linkages. The imported file corresponds to SVN revision 221843 (url
below) and is available under the terms of the New BSD license
(3-clause).

  http://svnweb.freebsd.org/base/head/sys/sys/queue.h?revision=221843

Signed-off-by: Avneesh Sachdev <avneesh@opensourcerouting.org>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>