+ * with DEAD_WEAK, and creates a new thread for the finalizer.
+ *
+ * This function is called just after GC. The weak pointers on the
+ * argument list are those whose keys were found to be not reachable,
+ * however the value and finalizer fields have by now been marked live.
+ * The weak pointer object itself may not be alive - i.e. we may be
+ * looking at either an object in from-space or one in to-space. It
+ * doesn't really matter either way.