update Changelog.txt
see
$Id: Changelog.txt,v 1.478 2021/05/21 22:03:13 nanard Exp $
+2021/08/11:
+ Detect Microsoft User-Agent: and force IGDv1 in that case
+
2021/06/18:
Fails on config parsing and init errors.
print errors during init to both syslog and stderr.
