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

Thanks to Florian Weimer and Eric Sesterhenn for reporting, reviewing
and testing.
int json_object_set_new(json_t *json, const char *key, json_t *value)
{
    if(!key || !utf8_check_string(key, -1))
    {
        json_decref(value);
        return -1;
    }

    return json_object_set_new_nocheck(json, key, value);
}

int json_object_set_new(json_t *json, const char *key, json_t *value)
{
    if(!key || !utf8_check_string(key, -1))
    {
        json_decref(value);
        return -1;
    }

    return json_object_set_new_nocheck(json, key, value);
}
