rem: struct hash_entry *bucket
add: struct hash_entry const *bucket
context: hash_lookup (const Hash_table *table, const void *entry){  struct hash_entry *bucket    = table->bucket + table->hasher (entry, table->n_buckets);  struct hash_entry *cursor;  assert (bucket < table->bucket_limit);  if (bucket->data == NULL)    return NULL;  for (cursor = bucket; cursor; cursor = cursor->next)    if (table->comparator (entry, cursor->data))      return cursor->data;  return NULL;}