[ODE] Performance patch : not checking collision between disabled bodies

[Nguyen Binh]

Hi Konstantin,

   After explore this thing more I found we better enable all bodies
   in dxStepBody, because all the velocity updates (even tiny) are the
   results of the solver to keep the system in good configuration.

   So in dxStepBody we just enable that body, i.e no check for big
   enough velocity.
   Thus, it's nearly the same with original implementation because in
   original, we enable all bodies that have joints (contacts) with
   enabled bodies, that's nearly the same (or actually the same?) with
   that bodies will move.

   I still not give up on improving box stacking in ODE. There are
   still something left to optimize. ;)

   Thanks all people for nice feedback!

-- 
Best regards,

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   Nguyen Binh
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   Glass Egg Digital Media
   
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