Add support for id ranges to XRC.

Allow to declare ranges of consecutive IDs in XRC by using the "id[n]" syntax.
Show this functionality in the xrc sample and test it in the new unit test.

Also show and test the "object reference" XRC functionality.

Closes #11431.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66059 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/xrc/xmlres.h

@@ -391,6 +391,8 @@ private:
 
     friend class wxXmlResourceHandler;
     friend class wxXmlResourceModule;
+    friend class wxIdRangeManager;
+    friend class wxIdRange;
 
     static wxXmlSubclassFactories *ms_subclassFactories;