Adjust speed vector in all 3 axis, so going downhill (mostly Y motion)

counts as going fast and is reduced, not just X and Z.


git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@5428 178a84e3-b1eb-0310-8ba1-8eac791a3b58

src/karts/kart.cpp

@@ -1202,6 +1202,7 @@ void Kart::updatePhysics(float dt)
 
         velocity.setZ( velocity.getZ() * velocity_ratio );
         velocity.setX( velocity.getX() * velocity_ratio );
+        velocity.setY( velocity.getY() * velocity_ratio ); // Up-down too
 
         getVehicle()->getRigidBody()->setLinearVelocity( velocity );