[ODE] get triangle index of a trimesh

[Bram Stolk]

Ettore Pancini wrote:
> I've tried dGeomTriMeshSetCallback and it works to an extent
> 
> just some notes:
> * there was a bug in the trimesh-sphere collider. solved by Geoff Carlton
> (http://q12.org/pipermail/ode/2005-March/015563.html). it seems is not
> applied to unstable, but i can confirm it works

Ok, now applied to unstable.

   bram