When calling setAutoDelete() on the implicitly shared copy of a list,
also auto-deletion of the original container was modified because
it was not detached. On the other hand, detach() was called by some
methods getting an Iterator parameter, which can lead to modification
of other implicitly shared copies but not the object is was called on.
This happens when the method is called on a not-already-detached
container, which is normally not the case because the container is
detached when the iterator is taken (e.g. calling begin()).
In such methods detach() cannot be called, and the client must
make sure that the iterator is taken after making an implicit copy.
This will NOT work:
List<int> l1 = { 1 };
auto it = l1.begin();
List<int> l2 = l1;
l1.erase(it);
This will modify both l1 and l2. The second and the third lines
must be swapped so that l1.begin() will detach l1 from l2.
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