made all XPM const to avoid warnings from mingw32 4.0 and adopt the code accordingly (patch 1872384)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@51228 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/widgets/itemcontainer.cpp

@@ -68,7 +68,7 @@ private:
 
 ItemContainerWidgetsPage::ItemContainerWidgetsPage(WidgetsBookCtrl *book,
                                                    wxImageList *image_list,
-                                                   char* icon[])
+                                                   const char *const icon[])
 : WidgetsPage(book, image_list, icon), m_trackedDataObjects(0)
 {
     m_items.Add(_T("This"));