Add a tested small GTK# sample

examples/gtk1.pl

@@ -0,0 +1,30 @@
+# Translated from http://www.mono-project.com/GtkSharp:_Hello_World
+
+constant $GTK = "gtk-sharp,Version=2.12.0.0,Culture=neutral,PublicKeyToken=35e10195dab3c99f";
+
+constant Application = CLR::("Gtk.Application,$GTK");
+constant Window      = CLR::("Gtk.Window,$GTK");
+constant Button      = CLR::("Gtk.Button,$GTK");
+
+Application.Init;
+
+# Set up a button object.
+my $btn = Button.new("Hello World");
+$btn.add_Clicked: sub ($obj, $args) { #OK
+    # runs when the button is clicked.
+    say "Hello World";
+    Application.Quit;
+};
+
+my $window = Window.new("helloworld");
+$window.add_DeleteEvent: sub ($obj, $args) { #OK
+    # runs when the user deletes the window using the "close
+    # window" widget in the window frame.
+    Application.Quit;
+};
+
+# Add the button to the window and display everything
+$window.Add($btn);
+$window.ShowAll;
+
+Application.Run;