rem: hash_lookup(void *_hash_table, const void *key)
add: hash_lookup(struct hash_table *table, const void *key)
context: hash_lookup(void *_hash_table, const void *key){	struct hash_table *t = (struct hash_table *)_hash_table;	void *i;	unsigned int hash;	if (t->compare_func == NULL)		return NULL;	hash = t->hash_func(NULL, key, t->table_size);	for (i = t->table[hash]; i != NULL; i = NEXT(t, i)) {		if (t->compare_func(i, key) == 0)			return i;	}	return NULL;}