clang 16: fix non-const lvalue reference error

wxNamingTree.cpp:94:45: error: non-const lvalue reference to type 'wxTreeItemIdValue'
 (aka 'void *') cannot bind to a value of unrelated type 'long'
  wxTreeItemId child = GetFirstChild( item, cookie);
                                            ^~~~~~

Author: saper

TAO/utils/wxNamingViewer/wxNamingTree.cpp

@@ -90,7 +90,7 @@ void WxNamingTree::clearChildren()
 
 void WxNamingTree::clearChildren( wxTreeItemId& item)
 {
-  long cookie;
+  wxTreeItemIdValue cookie;
   wxTreeItemId child = GetFirstChild( item, cookie);
   while( child) {
     clearChildren( child);