Drop some unused code

--HG--
extra : histedit_source : dc6e437512be7bed01ed3594bcc800974d85d788
Add a toList function, a test, and a bugfix

Inserting the keys ["a","b","c"] resulted in a structure that
answered lookup queries correctly, but contained duplicated
substructures :-(

--HG--
extra : amend_source : 8947d81648fb9b2d171110d88429f45c934af69f
extra : histedit_source : 9c2609bc0d62affcaa3711eadbb51590379df2d1