fix SupplyLow flag on give/take

[Keir Novik]

On Thu, 19 Oct 2000, Jim Kingdon wrote:

> If you really wanted SupplyLow to be more than a rough heuristic kind of
> thing, the player would need to be able to set how conservative they are
> (e.g. hitting a submarine on the way back may require you to go out of
> your way and no longer be in range), where they want to resupply a
> particular unit from, and the like. 

Don't we already have resupply-percent, rearm-percent, and repair-percent?

 - KN