Issue #20: Make AI not so chatty

The Combine AI had built-in anti-chatterbox code, so this was enabled
for the Rebels. I also increased the max delay before allowing more
talking from 3 to 5 seconds. These changes should completely eliminate a
single AI player from repeating themselves. (If you see this happen,
please tell me).

Note: If there are multiple teammate AI players in _different_ squads,
then they could still end up saying the same thing. Since there are
rarely more than 2-3 squads on one team playing in the same area, this
shouldn't be a big problem.