[boost] [inspect] Tag a directory to be ignored?

The Boost inspection tool that generates the inspection reports has a hardwired list of directories not to recurse into. "CVS", ".svn", ".git", etc. While those particular cases make sense, some of the hardwired names are so specialized ("doc/xml", "tools/build/v2/engine", etc.) that a better approach might be to tag directories as not to be inspected. That way the inspect.cpp code wouldn't have to be changed to accommodate yet another directory to be avoided. One simple way to do this would be for inspect.cpp to ignore any directories with some special file. For example, "no_boost_inspect". Comments? --Beman