[ODE] Trimesh preprocessing

[Colin Bonstead]

Just so I don't overlap work with anyone, I though I'd mention that I'm 
working on adding trimesh preprocessing, as detailed in the "Fast 
Contact Reduction for Dynamics Simulation" of Game Programming Gems 4.  
Basically it's just marking all the interior and concave edges as 
ignorable (and their vertices).

It requires 6 extra bytes of memory for each triangle (I'm using 8 for 
now to make it simpler).  It would be fairly easy to make it optional, 
if some people don't want it.  I'm doing this for work, so it should 
hopefully be done soon.  I'll submit a patch when I'm sure it's working 
well.

Colin Bonstead
Cyan Worlds, Inc