Introduce WarheadArgs

- Passes additional arguments to warheads on impact
- Uses that to reduce parameter count of DoImpact by 1

OpenRA.Mods.D2k/Warheads/DamagesConcreteWarhead.cs

@@ -10,6 +10,7 @@
 #endregion
 
 using System.Collections.Generic;
+using OpenRA.GameRules;
 using OpenRA.Mods.Common.Warheads;
 using OpenRA.Mods.D2k.Traits;
 using OpenRA.Traits;
@@ -23,11 +24,12 @@ namespace OpenRA.Mods.D2k.Warheads
 		[FieldLoader.Require]
 		public readonly int Damage = 0;
 
-		public override void DoImpact(Target target, Actor firedBy, IEnumerable<int> damageModifiers)
+		public override void DoImpact(Target target, WarheadArgs args)
 		{
 			if (target.Type == TargetType.Invalid)
 				return;
 
+			var firedBy = args.SourceActor;
 			var world = firedBy.World;
 			var layer = world.WorldActor.Trait<BuildableTerrainLayer>();
 			var cell = world.Map.CellContaining(target.CenterPosition);