set_proxy_menu_item
Description:
[ Version ( since = "2.4" ) ]
public void set_proxy_menu_item (string menu_item_id, Widget? menu_item)
  public void set_proxy_menu_item (string menu_item_id, Widget? menu_item)
Sets the MenuItem used in the toolbar overflow menu.
 The menu_item_id is used to identify the caller of this function and should also be used with 
      get_proxy_menu_item.
See also create_menu_proxy.
Parameters:
| this | 
           a ToolItem  | 
      
| menu_item_id | 
           a string used to identify   | 
      
| menu_item | 
           a MenuItem to use in the overflow menu, or null  |