* gc.c (slot_sweep, rb_gc_finalize_deferred)
(rb_objspace_call_finalizer, rb_gc): run finalizers
sequencially. [ruby-dev:44562]
* gc.c (rb_gc_finalize_deferred, rb_objspace_call_finalizer):
should use ATOMIC_EXCHANGE() to check the previous value.
[ruby-dev:44596] [Bug #5439]