new menu_set options: -parent and -is_hidden

So all types ahve the following options:
 -text "text"                        ("")
     Sets the visible text.
 -is_hidden false|true       (false)
     If the item currently should not appear in a menu.
 -parent id                  ()
     Sets the parent of this item.

Additionally menu_goto accepts an optional <parentid>
arg. (V.Boerchers)

server/commands/menu_commands.h

@@ -17,6 +17,7 @@ int menu_add_item_func (Client * c, int argc, char **argv);
 int menu_del_item_func (Client * c, int argc, char **argv);
 int menu_set_item_func (Client * c, int argc, char **argv);
 int menu_goto_func (Client * c, int argc, char **argv);
+int menu_set_main_func (Client * c, int argc, char **argv);
 
 #endif