natReference.cc (finalize_referred_to_object): Set `list->reference' to DELETED_REFERENCE when removing dead object.

	* java/lang/ref/natReference.cc (finalize_referred_to_object):
	Set `list->reference' to DELETED_REFERENCE when removing dead
	object.
	(find_slot): Added an assert.
	(DELETED_REFERENCE): New define.
	(add_to_hash): Check for DELETED_REFERENCE.
	(remove_from_hash): Just return if found slot isn't ours.

From-SVN: r70599