Limited-memory BFGS code by Ciyou Zhu, Richard Byrd, Peihuang Lu, and
Jorge Nocedal, which can be found (in various translations) at various
online sites:

	http://www.alglib.net/optimization/lbfgsb.php
	http://plato.asu.edu/ftp/other_software/toms778_f90.tar.gz

Unfortunately, since it was published in ACM TOMS, it seems to be
under the restrictive (semi-free) ACM copyright conditions.  This was
confirmed in a private email from the author, Prof. Nocedal.

Therefore, we no longer use this code in NLopt.

Fortunately, Prof. Luksan's PLIN.FOR code (see the luksan/ directory)
is an independent implementation of the same algorithm, and is licensed
under the LGPL.

UPDATE: Nocedal has apparently gotten permission from ACM to distribute
	his L-BFGS code under the terms of the GPL:

	http://www.eecs.northwestern.edu/~nocedal/lbfgsb.html

	Therefore, it seems possible to re-incorporate this code into
	NLopt, and I will look into this for a future release.
	However, that will put NLopt under the terms of the GPL, so I
	will need to keep it as an optional package.
