[gnome-chess] Update About dialog copyright notice

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 89ebce9788fb673ff069bf6c3c5a44113c002c0f
Author: Michael Catanzaro <mike catanzaro gmail com>
Date:   Sun Jul 14 19:58:08 2013 -0500

    Update About dialog copyright notice
    
    Robert's added 2010-2013 notices to the sources; his year can be updated
    in About as well.
    
    Also, add a notice for myself

 src/gnome-chess.vala |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/gnome-chess.vala b/src/gnome-chess.vala
index 93b2073..72f657b 100644
--- a/src/gnome-chess.vala
+++ b/src/gnome-chess.vala
@@ -1603,7 +1603,7 @@ public class Application : Gtk.Application
         about_dialog.modal = true;
         about_dialog.program_name = _("Chess");
         about_dialog.version = VERSION;
-        about_dialog.copyright = "Copyright 2010 Robert Ancell <robert ancell gmail com>";
+        about_dialog.copyright = "Copyright © 2010–2013 Robert Ancell\nCopyright © 2013 Michael Catanzaro";
         about_dialog.license_type = Gtk.License.GPL_2_0;
         about_dialog.comments = _("The 2D/3D chess game for GNOME. \n\nGNOME Chess is a part of GNOME 
Games.");
         about_dialog.authors = authors;