Improved output from locate_references(). Some more gc debug. Rev: src/gc.c:1.161 Rev: src/gc.h:1.78 Rev: src/mapping.c:1.127 Rev: src/multiset.c:1.36 Rev: src/object.c:1.174 Rev: src/program.c:1.338 Rev: src/security.c:1.31 Rev: src/threads.c:1.159