add hook for stance change notifications

OpenRA.Game/Network/UnitOrders.cs

@@ -189,6 +189,9 @@ namespace OpenRA.Network
 			p.Stances[target] = s;
 			if (target == w.LocalPlayer)
 				w.WorldActor.Trait<Shroud>().UpdatePlayerStance(w, p, oldStance, s);
+
+			foreach (var nsc in w.Queries.WithTrait<INotifyStanceChanged>())
+				nsc.Trait.StanceChanged(p, target, oldStance, s);
 		}
 	}
 }

OpenRA.Game/Traits/TraitsInterfaces.cs

@@ -229,4 +229,5 @@ namespace OpenRA.Traits
 	}
 
 	public interface INotifyKeyPress { bool KeyPressed(Actor self, KeyInput e); }
+	public interface INotifyStanceChanged { void StanceChanged(Player a, Player b, Stance oldStance, Stance newStance); }
 }