[development] The menu - does it have to be different on each page?

[Moshe Weitzman]

> Caching the whole rendered menu block would have some serious 
> performance implications.

unless i am missing something, this focus on rendering is misplaced. you 
still have calculate the whole menu tree to find the right path for callback 
and breadcrumb. thats where the performance cost is. building the rendering 
isn't too bad. furthermore, most big sites just disable navigation block and 
do own navigation using a different menu or separate from menu system.

now if we could determine callback without building the menu tree we would 
be in real fine shape.

-moshe