[Glade] Created branch glade-3-20

[Juan Pablo Ugarte <juanpablougarte gmail com>]

Hello everyone

I created a new Glade stable branch for GNOME 3.20 release named glade-
3-20

The fact that GNOME and Glade versions match up is pure coincidence and
perhaps from now on we will be able to keep up :)

thanks

Juan Pablo