Maxima 5.31.0 release



I've created branch-5_31 and tags branch-5_31-base and 5.31.0 in Git,
and created tar.gz and rpms and posted them to the SF file manager.
http://sf.net/p/maxima/files

Please give it a try. If someone can create a Windows installer, that
would be awesome.

best

Robert Dodier