[ODE] bending wheels again?

[Daniel.Groll@t-online.de]

Hi!

I made the wheel bending problem go away by adjusting the rotation of
the steering wheels every 6-10th timestep. I calculate which direction
they should have and set it with dBodySetQuaternion (or
dBodySetRotation). To prevent the car from turning over, I check if all
four wheels have contact with the ground. If yes, I apply small forces
to them as a "glue" and I reduce the angular velocity of the car body.
On an even surface it's almost impossible to tip over now. The
behaviour of the car when jumping or flying around seems to be ok
because the the tweaks are only applied when the car touches the ground
as said before.