code are:
++enum XML_Error +XML_UseForeignDTD(XML_Parser parser, XML_Bool useDTD) ++
This function allows an application to provide an external subset
+for the document type declaration for documents which do not specify
+an external subset of their own. For documents which specify an
+external subset in their DOCTYPE declaration, the application-provided
+subset will be ignored. If the document does not contain a DOCTYPE
+declaration at all and useDTD is true, the
+application-provided subset will be parsed, but the
+startDoctypeDeclHandler and
+endDoctypeDeclHandler functions, if set, will not be
+called. The setting of parameter entity parsing, controlled using
+XML_SetParamEntityParsing, will be honored.
The application-provided external subset is read by calling the
+external entity reference handler set via XML_SetExternalEntityRefHandler with both
+publicId and systemId set to NULL.
If this function is called after parsing has begun, it returns
+XML_ERROR_CANT_CHANGE_FEATURE_ONCE_PARSING and ignores
+useDTD. If called when Expat has been compiled without
+DTD support, it returns
+XML_ERROR_FEATURE_REQUIRES_XML_DTD. Otherwise, it
+returns XML_ERROR_NONE.
void XML_SetReturnNSTriplet(XML_Parser parser,