nsIBidirectionalIterator in Firefox 3.0

 Create a new iterator pointing to the same position in the underlying container or sequence to which this iterator currently points.
 The returned iterator is suitable for use in a subsequent call to |isEqualTo()| against this iterator.

 @result a new iterator pointing at the same position in the same underlying container or sequence as this iterator

 Retrieve (and |AddRef()|) the element this iterator currently points to.

 The result is undefined if this iterator currently points outside the
 useful range of the underlying container or sequence.

 @result a new reference to the element this iterator currently points to (if any)

 Test if |anotherIterator| points to the same position in the underlying container or sequence.

 The result is undefined if |anotherIterator| was not created by or for the same underlying container or sequence.

 @param anotherIterator another iterator to compare against, created by or for the same underlying container or sequence
 @result true if |anotherIterator| points to the same position in the underlying container or sequence

 Put |anElementToPut| into the underlying container or sequence at the position currently pointed to by this iterator.
 The iterator and the underlying container or sequence cooperate to |Release()|
 the replaced element, if any and if necessary, and to |AddRef()| the new element.

 The result is undefined if this iterator currently points outside the
 useful range of the underlying container or sequence.

 @param anElementToPut the element to place into the underlying container or sequence

 Move this iterator to the previous position in the underlying container or sequence.

 Advance this iterator to the next position in the underlying container or sequence.