Add XRC handler for wxAuiToolBar.

Also add the demonstration of AUI handlers (this one and the existing one for
wxAuiNotebook) to the xrc sample.

See #15686.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75271 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/doxygen/overviews/xrc_format.h

@@ -591,6 +591,23 @@ later only and you need to explicitly register its handler using
 @endcode
 to use it.
 
+@subsubsection xrc_wxauitoolbar wxAuiToolBar
+
+Building an XRC for wxAuiToolBar is quite similar to wxToolBar.
+The only significant differences are:
+@li the use of the class name wxAuiToolBar
+@li the styles supported are the ones described in the wxAuiToolBar class definition
+
+Refer to the section @ref xrc_wxtoolbar for more details.
+
+@note The XML Handler should be explicitly registered:
+@code
+    #include <wx/xrc/xh_auitoolb.h>
+
+    AddHandler(new wxAuiToolBarXmlHandler);
+@endcode
+
+@since 3.1.0
 
 @subsubsection xrc_wxbannerwindow wxBannerWindow