GC fixes. Made the gc quite a bit more whiny when -d is used.

Rev: src/array.c:1.68
Rev: src/array.h:1.19
Rev: src/gc.c:1.79
Rev: src/gc.h:1.38
Rev: src/mapping.c:1.79
Rev: src/mapping.h:1.24
Rev: src/multiset.c:1.20
Rev: src/multiset.h:1.10
Rev: src/object.c:1.120
Rev: src/object.h:1.45
Rev: src/program.c:1.232
Rev: src/program.h:1.87
Rev: src/svalue.c:1.72
Rev: src/threads.h:1.89