#12 cyclic index entries

[Anonymous]

It is possible to specify cycles in index entries, e.g.
"Kanonisches Recht" siehe auch "Kirchenrecht" and
"Kirchenrecht" siehe auch "Kanonisches Recht"

While this is in principle ok, it prevents such entries
being loaded again into benedetto, as the cyle isn't
recognized and benedetto will go into an endless loop
loading the entry.