* [ALEPH6,SC] Removed random_select/3: use lrabrary(random_ instead.
* [LIST_EXT,SC] Removed random_member/2 and random_select/2. Use library(random) instead.
* [LIST_EXT,SC] Rewrote random_list/2: much shorted code.
* [LIST_EXT,NEW] Added postfix/2 for symmetry with prefix/2.
* [LIST_EXT,SC] Removed remove_first[s]/2 and remove_last/2. Not deemed useful anymore.
* [LIST_EXT,NEW] Rewrote after/3 and before/3 to be the transitive closure of nextto/3, instead of a synonym.
* [RDF_TERM,SC] Full cleanup: removed several predicates that were not used.
* [SET_THEORY,SC] Rewrote random_subset/2, reusing random_sublist/2.
* [SET_THEORY,SC] Relocated transitive_closure/3 to DOYLE, too specific requirements for SET_THEORY.