allow marking things with AutoTargetIgnore so AutoTarget won't go for them

OpenRA.Mods.RA/AttackBase.cs

@@ -216,6 +216,7 @@ namespace OpenRA.Mods.RA
 
 			return inRange
 				.Where(a => a.Owner != null && self.Owner.Stances[a.Owner] == Stance.Enemy)
+				.Where(a => !a.HasTrait<AutoTargetIgnore>())
 				.Where(a => HasAnyValidWeapons(Target.FromActor(a)))
 				.OrderBy(a => (a.CenterLocation - self.CenterLocation).LengthSquared)
 				.FirstOrDefault();