Boost 1.28.0 released

Boost release 1.28.0 is available. See the www.boost.org home page for news of what's in the release, how to download, and how to build. (Remember that only the Python, Regex, and Thread libraries currently require a build; the others are entirely implemented in the headers.) This is a major release, with both new libraries and lots of general improvements. Much effort has gone into smoothing out the build process for those who use the Python, Regex, and Thread libraries. Among other changes, the release .zip and .tar.gz files are being built via a new procedure, using CVS export. Please let me know right away if you have any problems with either file. --Beman