This is the main bulk of this boolification work, but although it's
making the largest actual change, it should also be the least
disruptive to anyone interacting with this code base downstream of me,
because it doesn't modify any interface between modules: all the
inter-module APIs were updated one by one in the previous commits.
This just cleans up the code within each individual source file to use
bool in place of int where I think that makes things clearer.
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]
