Description

   To delete a library module, first call LBR$DELETE_KEY to delete
   all keys that point to it. If no library index keys are pointing
   to the module header, LBR$DELETE_DATA deletes the module header
   and associated data records; otherwise, this routine returns the
   error LBR$_STILLKEYS.

   Note that other library routines can reuse data blocks that
   contain no data.