[development] Resetting Drupal's menu cache

Hi all, I've noticed that when you make a change to your MODULE_menu hook, that you need to disable and re-enable the module before the changes are made effective. This is fine for my module because I can do that, but I want to make a change to a core module (for example, make the weight of Logout 1000 so it is always at the bottom). The menu module is a core module and cannot be disabled, so how do I reset this menu cache for core modules? -Matt