[polyml] Release of version 5.1

I've now installed the official release of Poly/ML 5.1 on sourceforge. I'll update the web site shortly. As well as the various fixes and updates I mentioned earlier, such as threading and saving state, there were also some last-minute fixes to get Poly/ML working on the new Mac OS X release.

There are a few minor bugs that were reported that I have held over to the next release rather than risk breaking existing code. I'll add the fixes to CVS. That version will become a testing release of 5.2.

It would be helpful to be kept aware if anyone is planning to package Poly/ML for any of the distributions just to keep track of them and to avoid duplication of effort.

David.