VarAction2: Detect and replace scaled reads of train/RV/ship current speed

src/newgrf_extension.h

@@ -60,6 +60,7 @@ enum Action0RemapPropertyIds {
 enum Action2VariableRemapIds {
 	A2VRI_OBJECT_FOUNDATION_SLOPE = 0x100,
 	A2VRI_OBJECT_FOUNDATION_SLOPE_CHANGE,
+	A2VRI_VEHICLE_CURRENT_SPEED_SCALED,
 };
 
 /** Action14 feature definition */