CVE-2013-6401: Change hash function, randomize hashes

Thanks to Florian Weimer and Eric Sesterhenn for reporting, reviewing
and testing.
static void json_delete_object(json_object_t *object)
{
    hashtable_close(&object->hashtable);
    jsonp_free(object);
}

static void json_delete_object(json_object_t *object)
{
    hashtable_close(&object->hashtable);
    jsonp_free(object);
}
