Check menu sub tree permissions recursively when editing a node

This change has already been made in CVS but it isn't available in the current download so I'm including it here for people who might be looking.
The behavior it fixes looks like this:
You can create new menu items as you would expect. But when you go back to edit a node you will only be able to alter its menu item if it is an immediate child of a menu item you have permission to. This change allows the recursion to work as intended. IE, If the menu item is a descendant of one you have permission to edit then you will be able to edit it.