optional ProductionQueueSpeedup with integer math to avoid potential desyncs

ClassicProductionQueue.cs

	public class ClassicProductionQueueInfo : ProductionQueueInfo, Requires<TechTreeInfo>, Requires<PowerManagerInfo>, Requires<PlayerResourcesInfo>
	{
		public readonly bool SpeedUp = false;
		public readonly int BuildTimeSpeedUpDivisor = 2;
		public readonly int MaxBuildTimeReductionSteps = 6;

		public override object Create(ActorInitializer init) { return new ClassicProductionQueue(init.self, this); }
	}

[...]

		public override int GetBuildTime(String unitString)
		{
			var unit = Rules.Info[unitString];
			if (unit == null || ! unit.Traits.Contains<BuildableInfo>())
				return 0;

			if (self.World.LobbyInfo.GlobalSettings.AllowCheats && self.Owner.PlayerActor.Trait<DeveloperMode>().FastBuild)
				return 0;

			var selfsameBuildings = self.World.ActorsWithTrait<Production>()
				.Where(p => p.Trait.Info.Produces.Contains(unit.Traits.Get<BuildableInfo>().Queue))
				.Where(p => p.Actor.Owner == self.Owner).ToArray();

			var time = (int) (unit.GetBuildTime() * Info.BuildSpeedModifier);

			if (Info.SpeedUp && selfsameBuildings.Count() > 1)
				for (int i = 1; i < Info.MaxBuildTimeReductionSteps; i++)
					time /= Info.BuildTimeSpeedUpDivisor;

			return time;