Introduced btActionInterface. This makes it easier to extend user-defined actions, such as vehicles and characters.

btRaycastVehicle and btKinematicCharacterController are derived from btActionInterface now.
Some cosmetic cleanup: changed sourceforce/sf.net url to bulletphysics.com.

src/BulletDynamics/Dynamics/btContinuousDynamicsWorld.cpp

@@ -90,8 +90,7 @@ void	btContinuousDynamicsWorld::internalSingleStepSimulation( btScalar timeStep)
 	integrateTransforms(timeStep * toi);
 
 	///update vehicle simulation
-	updateVehicles(timeStep);
-
+	updateActions(timeStep);
 
 	updateActivationState( timeStep );