HTMLParser: start working on xml mode
added methods:
Status parse_xml_file(const char * file_name, Space & out_space, bool compact_mode = false, bool clear_space = true);
Status parse_xml_file(const std::string & file_name, Space & out_space, bool compact_mode = false, bool clear_space = true);
Status parse_xml_file(const wchar_t * file_name, Space & out_space, bool compact_mode = false, bool clear_space = true);
Status parse_xml_file(const std::wstring & file_name, Space & out_space, bool compact_mode = false, bool clear_space = true);