* [FUNCTION,SC] Cleanup.
* [POSET,NEW] New module for poset support. Currently only containing trivial predicates.
* [RELATION,NEW] New module and big cleanup of predicates expressing properties of and transformations on relations.
* [SET_THEORY,SC] Relocated closure/4 for calculating closure over sets according to a specified goal.
* [GRAPH_THEORY,SC] Make more reuse of existing predicates in SET_THEORY and PAIR_EXT.
* [PAIR_EXT,NEW] Added inverse_pair/2, pair/3, pair_element/2.
* [PL_MODE,NEW] Rewrote call_complete/3, simplifying things quite a bit.
* [RELATION,SC] Simplified equivalence_class/3: one less argument.
* [RELATION,NEW] Rewrote all closures to use the new closure/3 predicate in SET_THEORY.
* [SET_THEORY,NEW] Rewrote closure/3 for calculating arbitrary closures over objects and sets.