private void readNotationDecl()
private void readNotationDecl(boolean inExternalSubset)
  private void readNotationDecl()    throws IOException, XMLStreamException  {    requireWhitespace();    String notationName = readNmtoken(true);    if (notationName.indexOf(':') != -1)      error("Illegal character ':' in notation name", notationName);    requireWhitespace();    ExternalIds ids = readExternalIds(true, false);    ids.notationName = notationName;    doctype.notations.put(notationName, ids);    skipWhitespace();    require('>');  }