Firefox Gtk3 test package

[Michael Cronenworth]

H. Guémar wrote:
> What's the point ? There's absolutely no benefit in keeping Gtk+2 longer.
> Gtk+ 2.24.0 has been released 3 years ago (january, 2011) and is only receiving
> bugfix due to existing apps who didn't move to Gtk+3.
> By migrating more apps, we can drop Gtk+ 2.24 (at least from images), firefox is
> one of the major application that prevents us to do so.

You'll never (in the foreseeable future) be able to drop GTK2. Firefox will 
still need it to run NSAPI plugins.