the legacy style is a poorly executed attempt at Maildir++, so introduce
the latter for the sake of completeness. but most users will probably
just want to use subfolders without any additional dots.
as opposed to earlier threats, BerkDB was not entirely dropped; i
suppose the isync 0.7 -> 0.8 change had a reason, so i added an
alternative UID storage scheme.
note that BDB 4.0 is not sufficient, as the db->open function changed in
an incompatible way ...
i updated the debian packaging except for a changelog entry.
note that i removed the upgrade blurb, as upstream now has a smooth
upgrade path down to at least isync 0.4.
