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

Thanks to Florian Weimer and Eric Sesterhenn for reporting, reviewing
and testing.
void *hashtable_iter_key(void *iter)
{
    pair_t *pair = list_to_pair((list_t *)iter);
    return pair->key;
}

void *hashtable_iter_key(void *iter)
{
    pair_t *pair = list_to_pair((list_t *)iter);
    return pair->key;
}
