Update to SGI FreeB 2.0.

Update to SGI FreeB 2.0.

Under the terms of version 1.1, "once Covered Code has been published
under a particular version of the License, Recipient may, for the
duration of the License, continue to use it under the terms of that
version, or choose to use such Covered Code under the terms of any
subsequent version published by SGI."

FreeB 2.0 license refers to "dates of first publication".  They are here
taken to be 1991-2000, as noted in the original license text:

 ** Original Code. The Original Code is: OpenGL Sample Implementation,
 ** Version 1.2.1, released January 26, 2000, developed by Silicon Graphics,
 ** Inc. The Original Code is Copyright (c) 1991-2000 Silicon Graphics, Inc.
 ** Copyright in any portions created by third parties is as indicated
 ** elsewhere herein. All Rights Reserved.

Official FreeB 2.0 text:

http://oss.sgi.com/projects/FreeB/SGIFreeSWLicB.2.0.pdf

As always, this code has not been tested for conformance with the OpenGL
specification.  OpenGL conformance testing is available from
http://khronos.org/ and is required for use of the OpenGL logo in
product advertising and promotion.