[Vala] GTKBuilder example doesn't work

[Damien Radtke <damienradtke gmail com>]

Using valac version 0.12.0, the example at this page doesn't work:

https://live.gnome.org/Vala/GTKSample#Loading_User_Interface_from_XML_File

I can load the interface fine, but I get errors saying that none of the
signal handlers can be found. Any idea why this wouldn't work?

~Damien