Yikes! I've only just noticed that this copy of tree234.c was still

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.

git-svn-id: svn://svn.tartarus.org/sgt/puzzles@6388 cda61777-01e9-0310-a592-d414129be87e