Initial commit of a basically working but severely unpolished

utility which does "du" only more usefully: its key feature is that
it breaks down your disk space usage simultaneously by subdirectory
and by atime, so that you can identify large chunks of data which
are simply gathering dust.

git-svn-id: svn://svn.tartarus.org/sgt/agedu@8224 cda61777-01e9-0310-a592-d414129be87e