dateMenu: Make sure that the event list fills the available width

Currently the menu has a hardcoded width which result into the hover
effect of the "Open Calendar" item being "cut off" in the middle rather
then reaching to the edge.

To be consistent with other menu items, make it expand to fill the available
space.

js/ui/dateMenu.js

@@ -104,10 +104,10 @@ DateMenuButton.prototype = {
         // Fill up the second column
 
         vbox = new St.BoxLayout({vertical: true});
-        hbox.add(vbox);
+        hbox.add(vbox, { expand: true });
 
         // Event list
-        vbox.add(this._eventList.actor);
+        vbox.add(this._eventList.actor, { expand: true });
 
         item = new PopupMenu.PopupMenuItem(_("Open Calendar"));
         item.connect('activate', Lang.bind(this, this._onOpenCalendarActivate));