network improvements

[Jim Kingdon]

> Thus, we might have a unit->acted flag that is set by broadcast_action
> and reset by run_game. There are several merits to this scheme:

I think I like it.

> The key question is if there is any situation where more than one
> action per unit and run_game execution should be allowed.

Well, as a human player you might *like* to be able to queue up
actions if response is slow, but it doesn't really work.  There is
always "oh, there was a submarine in the way" or other similar things.
So I don't think this is a case where we want more than one action
piled up.  Nor am I thinking of other situations.