Report an XML comment anywhere in the document.
This callback will be used for comments inside or outside the document element, including comments in the external DTD subset (if read). Comments in the DTD must be properly nested inside start/endDTD and start/endEntity events (if used).
@param ch An array holding the characters in the comment.
@param start The starting position in the array.
@param length The number of characters to use from the array.
@exception SAXException The application may raise an exception.