[ut2004] Demos Create AVI option

[Gian Paolo Mureddu]

>
> typ 'demoplay <demoname> in your console while in-game?
> why convert it? =)
> (if it's just for "evaluating")
>
> -ups
>
>
To see it in a machine that does not have UT installed? To burn that 
into a CD which I can convert into a VCD and play it on my TV? Basically 
for those motives...