Fixes to the AI build code

[Jim Kingdon]

> I have also removed the oplayer AI, which was never used the way it was
> supposed to (as a development tool for the mplayer).

I was trying to use it in exactly that fashion this morning.

Now, the problem was that I was using the standard game, and vagueries
in map generation were a stronger factor in success than AI strategy
(especially fine points thereof).

So I'm not sure I'm really arguing in favor of keeping oplayer, but I
did bristle at "never" ;-).