Avoid use of C++11 range-based for loop in wxOSX code

This results in clang -Wc++11-extensions warning if -std=c++1x (for some
value of "x") is not used.

src/osx/cocoa/menu.mm

@@ -361,8 +361,11 @@ public :
         [m_osxMenu setAutoenablesItems:NO];
         
         wxMenu* menu = GetWXPeer();
-        for ( auto item : menu->GetMenuItems() )
+        for ( wxMenuItemList::compatibility_iterator node = menu->GetMenuItems().GetFirst();
+              node;
+              node = node->GetNext() )
         {
+            const wxMenuItem* const item = node->GetData();
             if ( item->IsSubMenu() )
             {
                 wxMenuCocoaImpl* subimpl = dynamic_cast<wxMenuCocoaImpl*>(item->GetSubMenu()->GetPeer());