[development] if you change your menu definition

[Karoly Negyesi]

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.