Add support for icons in wxAUI panes title bars.

Add wxAuiPaneInfo::Icon() method and shows its use in the sample.

Closes #12856.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66670 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/aui/dockart.h

@@ -130,6 +130,10 @@ public:
                   const wxRect& rect,
                   wxAuiPaneInfo& pane);
 
+    void DrawIcon(wxDC& dc,
+                  const wxRect& rect,
+                  wxAuiPaneInfo& pane);
+
 protected:
 
     void DrawCaptionBackground(wxDC& dc, const wxRect& rect, bool active);