Use decimal instead of long for WPos offset

To remove overflow risk.

OpenRA.Game/WPos.cs

@@ -64,8 +64,8 @@ namespace OpenRA
 				return ret;
 
 			// Add an additional quadratic variation to height
-			// Attempts to avoid integer overflow by keeping the intermediate variables reasonably sized
+			// Uses decimal to avoid integer overflow
-			var offset = (int)(((((((long)(b - a).Length * mul) / div) * (div - mul)) / div) * pitch.Tan()) / 1024);
+			var offset = (int)((decimal)(b - a).Length * pitch.Tan() * mul * (div - mul) / (1024 * div * div));
 			return new WPos(ret.X, ret.Y, ret.Z + offset);
 		}