* improved: when encoding utf8 text into us-ascii xml, use character entity references for characters number 0-31
(ascii non printable characters), as we were already doing when encoding iso-8859-1 text into us-ascii xml
* improved: when encoding utf8 text into us-ascii xml, use character entity references for characters number 0-31
(ascii non printable characters), as we were already doing when encoding iso-8859-1 text into us-ascii xml