Add a more complete example of different controls variants in XRC.

Add a dialog showing all the existing variants of a few common controls to
allow seeing at a glance how do they look.

See #16247.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77002 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/xrc/rc/menu.xrc

@@ -79,6 +79,11 @@
             <bitmap>variable.xpm</bitmap>
             <help>Replace variables in the XRC file at runtime</help>
         </object>        
+        <object class="wxMenuItem" name="variants">
+            <label>_Variants</label>
+            <bitmap>variants.xpm</bitmap>
+            <help>Show different controls variants</help>
+        </object>
         <object class="wxMenuItem" name="recursive_load">
             <label>_Recursive Load</label>
             <help>Show how an individual control can be loaded</help>