A utility class for storing a list of external references.  An external reference is
 * a PDOMName that references a PDOMBinding in a different linkage.  This list can be
 * examined using {@link #getIterator()}.
A utility class for storing a list of external references.  An external reference is
 * a PDOMName that references a PDOMBinding in a different linkage.  This list can be
 * examined using {@link #getIterator()}. | PDOMExternalReferencesList.java