Fri Apr  3 10:53:49 EST 1998
  Update to reflect lp_solve version 2.2 (by changing "2.0" to "2.2"
in various places).  Return solve_result_num and .sstatus to AMPL.
(Unfortunately, there seems to be no way to suggest a starting
basis to lp_solve.)  Shift variables with negative lower bounds
to reflect lp_solve's restriction to variables with nonnegative
lower bounds.

Tue Jul 28 22:30:00 EDT 1998
  README: add table of possible solve_result_num values.

Sun Nov 14 18:21:48 EST 1999
  README, lpsolve.c, makefile: adjust for version 3.0; should future
versions of lp_solve appear, it may suffice to change the LPSOLVE =
line in the makefile to point to the directory for the version of
interest.

Thu Nov 18 16:02:45 EST 1999
 lpsolve.c: portability tweak: change (int) to Intcast.
 makefile: renamed makefile.u (for Unix); makefile.vc added.

Thu Feb  3 22:39:16 EST 2000
  makefile.vc: adjusted reflecting changes to ../makefile.vc.

Tue Oct  3 00:28:07 EDT 2000
  lpsolve.c: fix bug in supplying variable bounds in problems
involving some free variables (-Infinity <= var <= +Infinity)
followed by variables with finite nonzero bounds.  Example:
steelpl5.mod + steelpl5.dat in the AMPL book.

Wed Apr 10 14:30 EDT 2002
  lpsolve.c: use sos_add() and sos_finish() to handle .sosno and .ref;
add "version" keyword.
  makefile.*: adjust for lp_solve_3.2.

Tue May  7 16:36:21 EDT 2002
  More tweaks to "version" for consistency with other solvers.

Thu Feb  7 13:14:00 EDT 2002
  lpsolve.c: use sos_add() and sos_finish() to handle .sosno and .ref;
add "version" keyword.
  makefile.*: adjust for lp_solve_3.2.

Fri Feb 28 19:03:12 EST 2003
  Update for lp_solve_4.0 (lpsolve.c still works with 3.x).

Fri Mar 28 16:06:14 EST 2003
  README:  mention lpsolve_options.

Thu Jun 12 23:33:02 EDT 2003
  Adjust so "lpsolve" (no arguments) shows usage rather than faulting.

20120719
  Change name of lpsolve.c to lpsolve4.c, of makefile.u to makefile4.u,
and makefile.vc to makefile4.c.  New lpsolve.c, makefile.u, and makefile.vc
that work with LP_SOLVE 5.5.2.  Updates to README.  Rule for xsum.out
is now just in makefile.u.

20120720
  lpsolve5.c: fix glitches in returning solutions.

20151211
  lpsolve5.c: fix a bug (possible fault; wrong values) in returning
suffix .sstatus values.