[development] if you change your menu definition

And then you want to have some effect then in the past you emptied cache_menu. In HEAD that achieves particularly little as that table is currently unused and we might even drop it. Go to a settings page and press save. That runs menu_rebuild. (There are other pages but this is the simplest) I guess devel module will also get a menu_rebuild button or something soon if it does not have it already.