[ODE] Modifying the hinge example to add collisions

[join at krakendev.com]

Hello,
   I couldn't find this question elsewhere, and the sample that I think
would help, chain2, uses a direct interface to the world which I can't
duplicate.

Basically, I'm set up with a 6 geoms and the corresponding bodies in a
space. These are in turn split up into 2 groups of 3 bodies with 2 hinges.
The collision code from the buggy example serves me fine (save the low
number of contacts) for the two chains not falling through the ground.
However, I'm wondering how to enable this collision to extend to within
the jointed bodies as well. Any help would be greatly appreciated.