Fire in the hole!

Many thanks to Olivier Crête, we now have a nice small library for firing holes through firewalls using a part of UPnP IGD API. This library also provides a convenient way to do all that without having to use a gmainloop. While Olivier will most probably use it in his farsight2, I am sure this will be useful for other projects (I did not say Ekiga :)) as well.