[quake3] feature: advanced demo navigation

[Erik Kloppenburg]

Neil Toronto wrote:
> This can be as easily done in a mod as in the engine. If the engine did 
> it, it would do basically the same thing. One good argument for doing it 
> in a mod is that the mod can better control who is allowed to make an 
> MVD. Recordin

What if it were serverside only? Server knows already everything that's 
going on, so there's no extra risk then.