UPBGE: Fix unormalized vehicle axis direction.

Previously the user was able to specify a unormalized axis direction
for wheel and suspension in a vehicle wrapper, but bullet doesn't handled
it properly and generated odd wheel angles.

To fix this issue we ensure that the axis direction are well normalized.

Fix second part of issue: #593.

source/gameengine/Physics/Bullet/CcdPhysicsEnvironment.cpp

@@ -221,8 +221,8 @@ class WrapperVehicle : public PHY_IVehicle
 	    float wheelRadius,
 	    bool hasSteering)
 	{
-		btWheelInfo& info = m_vehicle->addWheel(ToBullet(connectionPoint), ToBullet(downDirection), ToBullet(axleDirection),
-		                                        suspensionRestLength, wheelRadius, gTuning, hasSteering);
+		btWheelInfo& info = m_vehicle->addWheel(ToBullet(connectionPoint), ToBullet(downDirection.normalized()),
+				ToBullet(axleDirection.normalized()), suspensionRestLength, wheelRadius, gTuning, hasSteering);
 		info.m_clientInfo = motionState;
 	}