XSB Src (SVN)-old

Added tests of new prolog_db set operations.

Added documentation of new prolog_db set operations.

Added new predicates for set operations on DBs: union, intersection,
set difference, symmetric difference, subset, disjoint. These are all
implemented using the structure of the trie representation.

sym = insert_psc(ptoc_string(CTXTc 1),(int)ptoc_int(CTXTc 2), global_mod, &value);
init_psc_ep_info(pair_psc(sym)); // reset to reload
psc_set_data(pair_psc(sym),(Psc)makestring(string_find(mod_name,1)));
+ // psc_set_env(tpsc,T_UNLOADED);
+ if (get_type(pair_psc(sym)) == 0)
+ psc_set_type(pair_psc(sym),T_UDEF);
} else {
mod_psc = pair_psc(insert_module(0, mod_name));
sym = insert_psc(ptoc_string(CTXTc 1), (int)ptoc_int(CTXTc 2), mod_psc, &value);

Added the 3 +'d lines above to psc_import to make the import directive
consistent with the import declaration as executed by the loader. The
motivation for this is to make predicates that are imported but
undefined have the type T_UDEF, which can be reflected as unloaded by predicate_property.

Added documentation for get_calls/4 which returns the pointer to the
call node; get_calls/3 is still supported as a standard predicate.

Documentation of subgoal property plus other small changes.

Added a new -- very simple test for subgoal_property/2.

A bit of code restructuring.

A couple I forgot.

Added gc_strings to go with gc_heap, etc. Mostly for debugging.