Convert AnimationWithOffset to world coords.

Animations (via Actor.CenterPosition) now
understand Altitude, so there is potential for
mis-positioned animations if any existing altitude
hacks were missed.

OpenRA.Game/Traits/Render/RenderSimple.cs

@@ -57,7 +57,8 @@ namespace OpenRA.Traits
 		public Animation anim
 		{
 			get { return anims[""].Animation; }
-			protected set { anims[""].Animation = value; }
+			protected set { anims[""] = new AnimationWithOffset(value,
+				anims[""].OffsetFunc, anims[""].DisableFunc, anims[""].ZOffset); }
 		}
 
 		public static string GetImage(ActorInfo actor)