[boost] [1.35.0] Attention library maintainers: Broken links

I've fixed dozens of the most obvious broken links in Boost.Test documentation, both trunk and release branch. There are still 20 or so broken links left. I find it pretty irritating when the release manager and other volunteers have to fix a library's broken links. This is something that maintainers should check periodically, and fix themselves. The Boost "inspect" tool can be run in any directory to find broken links and other problems in that directory and its sub-directories. That makes it easy to check potential fixes without waiting for the full inspection report to cycle. --Beman