[development] Menu system work

[Karoly Negyesi]

> You'll want to bump that 20 to 2000 or so.  I'm a bit disappointed by  
> the results of HEAD.  It's faster, but not much.  I was under the  
> impression that the biggest win of the new menu system would be a  
> nice performance gain ...

The menu system is indeed faster, the navblock is not or not significantly, but it's not slower either.I guess we will end up around 5-10% faster than D5.

The big gains are a maintainable menu.inc . There are bugs in the old menu system which are unfixable. There are bugs which are probably fixable but needs rha/jonbob both of whom are mostly missing from the project.Also,  !$may_cache is a mess.