add new long WRange.RangeSquared to avoid integer overflows

OpenRA.Game/WorldUtils.cs

@@ -36,9 +36,8 @@ namespace OpenRA
 			{
 				// Target ranges are calculated in 2D, so ignore height differences
 				var vec = new WVec(r, r, WRange.Zero);
-				var rSq = r.Range * r.Range;
 				return world.ActorMap.ActorsInBox(origin - vec, origin + vec).Where(
-					a => (a.CenterPosition - origin).HorizontalLengthSquared <= rSq);
+					a => (a.CenterPosition - origin).HorizontalLengthSquared <= r.RangeSquared);
 			}
 		}