Untie all items in itemList. For each item in the item list, if the usage counter for that item is greater than 1 then it is cloned, the original shared item is replaced by the cloned copy and the usage count of the shared item is reduced by 1. If the usage count is already 1, the associated macro is simply deleted and the usage count set to 0 to indicate an unshared item. Note that it is not possible to untie a pdf since these are not actually shared [see the Tie (TI) command above].