Description

   If LBR$DELETE_KEY finds the key specified by key_name in the
   current index, it deletes the key. Note that if you want to
   delete a library module, you must first use LBR$DELETE_KEY to
   delete all the keys that point to it, then use LBR$DELETE_DATA to
   delete the module's header and associated data. You cannot call
   LBR$DELETE_KEY from within the user-supplied routine specified in
   LBR$SEARCH or LBR$GET_INDEX.