Kevin Lyles spotted a tree234 bug! copytree234() segfaulted when
asked to copy a tree containing no elements, due to failing to allow
for the case that t->root might be NULL. Fixed, and added a
regression test.
[originally from svn r7092]
using unwrappered malloc/free, leaving plenty of openings for out-
of-memory segfaults. Switch to using Puzzles's memory management,
which I should have done right at the start but can only assume I
forgot about.
[originally from svn r6388]
