libxml++: New API in libxml++ 2.24

Member xmlpp::Element::add_child_text (xmlpp::Node* previous_sibling, const ustring& content=ustring())
Member xmlpp::Element::add_child_text_before (xmlpp::Node* next_sibling, const ustring& content=ustring())
Member xmlpp::SaxParser::parse_chunk_raw (const unsigned char* contents, size_type bytes_count)