Migrate the rest of tests/ to GPLv3. - drag 'n drop was also done by Oliver Graf, so samy copyright - with gtk-test.glade, the only question was where to actually stick the attribution; inserted XML comment

# Force the window background to be the same as the default face background:
# white.

style "default_background"
{
	bg[NORMAL] = { 1.0, 1.0, 1.0 }
}

class "GtkXEmacs" style "default_background"