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

Thanks to Florian Weimer and Eric Sesterhenn for reporting, reviewing
and testing.
int json_object_del(json_t *json, const char *key)
{
    json_object_t *object;

    if(!json_is_object(json))
        return -1;

    object = json_to_object(json);
    return hashtable_del(&object->hashtable, key);
}

int json_object_del(json_t *json, const char *key)
{
    json_object_t *object;

    if(!json_is_object(json))
        return -1;

    object = json_to_object(json);
    return hashtable_del(&object->hashtable, key);
}
