void list_all_changes(const change_list &c) {
  for (list<owl_diff::change>::const_iterator itr = c.begin(); itr != c.end(); ++itr) {
    list_change(*itr);
  }
}
// note: may need to remove reference from b, as the STL doesn't
// seem to like this.
inline void splice_changes(change_list &a, change_list b) {
  a.splice(a.end(), b);
}