named_livings - return all living objects with names

mapping named_livings();

named_livings() returns all objects that have called both set_living_name()
and enable_commands().  It is significantly more efficient than livings().

named_livings() is available if PACKAGE_CONTRIB is defined, and NO_ADD_ACTION
is not.

 Tim Hollebeek  Beek@ZorkMUD, Lima Bean, IdeaExchange, and elsewhere
