[ODE] 16 bits indices and TriMesh

[Joe Ante]

> Is there any other way working around this problem than me cloning
> indexbuffers or changing my renderingengine to using 32bits indices instead of
> 16bits?
You can enable MeshInterface callbacks by defining
#define OPC_USE_CALLBACKS

And then changing the trimesh code to setup the callbacks to generate the
triangle vertices.

If performance is a problem it might be worth making a new #define in
MeshInterface and changing the mesh data to shorts.

Joe Ante