XSB Src (SVN)-old

Since I needed to use AVL trees, I took a few minutes out to document assoc.P, the libary that contains this functionality.

Initial test for tripwires.

Initial commit for tripwires

Initial commit for tripwire handling for large number of subgoals / large number of SCCs.

Micro optimization of lattice and fold aggregation in case of all true
answers. This gives maybe a 5-8% improvement in time for intensive
aggregations of true answers.

Fixed aggregation so lattice and fold now work with undefined answers.
This restores the functionality that Teri introduced, but in which we
found a bug. It also extends it to fold. It detects if no undefs
occur and uses the earlier more efficient version in that case. There
is some overhead for the checking but it is small compared to always
assuming undefineds occur.

It should be noted that producing all possible undef answers can be
combinatorically explosive, so care should be taken when using this
option.

Removed code that hasn't been used in years (old_excess_vars/4)

memory_xsb.c: print warning if double-freeing instead of crashing
biassert.c: clean up after retracting to avoid reusing garbage and ultimately crashing.

Updated insert_psc to make set_env field conditional on whether
the symbol is defined in usermod or not.

fixed psc_insert to initialize a couple of psc fields: data and env_type
(for which T_IMPORT doesn't work, so used T_GLOBAL; hopefully OK.)