ddns.cgi: Check for valid FQDN before doing nslookup.

We now check if the used hostname is a valid FQDN before doing the nslookup to
determine if a DDNS host is up do date.
tor: Update to 0.2.4.23

http://www.heise.de/security/meldung/Erfolgreicher-Angriff-auf-Tor-Anonymisierung-2278774.html