XSB Src (SVN)-old

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.)

Fixed read_canonical and write_canonical to handle a() forms.

Note: read_canonical will *not* recognize a( ), i.e. with a whitespace
between the parens. Since this is read_canonical (and write_canonical
produces the accepted form,) I think this is OK. It's a more
complicated fix if we were to accept the form with the whitespace.

Fixed atom(a()) to fail, and compound(a()) to succeed.
(Had been intentionally programmed to be the opposite, for some reason.
System self-compiles and all tests pass with this change. It is now
consistent with SWI's implementation of the f() form.)

cleanup in dbdrivers package

Minimal documentation for table_index directive. (There may be a better
place in the manual for this? And it needs to be expanded if it stays.)

Minor fix to concat_atom to handle integers more consistently.

Added code to support table_index directive (abolish_table_index_pred)

New table_index directive to use subsumptive tables to do more general
indexing of tables.