More rtldebug to get better info when gc_mark problems happen. Rev: Makefile:1.168 Rev: src/array.c:1.226 Rev: src/gc.c:1.338 Rev: src/gc.h:1.138 Rev: src/mapping.c:1.214 Rev: src/multiset.c:1.119 Rev: src/object.c:1.304 Rev: src/pike_types.c:1.361 Rev: src/program.c:1.773 Rev: src/svalue.c:1.255