gtk3-gi test: add Gtk::GestureSingle tests
gtk3-gi test: add Gtk::GestureSingle tests

Since GTK+3 3.14 GtkGestureSingle is supported.
ref: https://developer.gnome.org/gtk3/3.14/GtkGestureSingle.html

kitachro/ruby-gnome2,kitachro/ruby-gnome2,kitachro/ruby-gnome2,kitachro/ruby-gnome2,kitachro/ruby-gnome2