(PR#10952) AI doesn't settle with high techlevel

<URL: http://rt.freeciv.org/Ticket/Display.html?id=10952 >

> So I guess we should WAG up settlers before happysize is reached so that
> settlers win over wonders, attack units and other useless fluff every
> time until we manage to grow.
> 
>   - Per
Beware of this. It used to be possible to stump an AI if you attacked it
too soon. It is no good to build settlers while being smashed. I don't
want the AI to go that way again.

However, overpowering wonders is a good idea.