Merge branch 'xchat-url-handler' into 'belenos'

Add make-xchat helper

This helper uses [this patch](https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=691477#28) to replace the reference to a nonfree browser (Opera) with a reference to the default system browser (x-www-browser). It should work on toutatis too.

See merge request !100