[ODE] 16 bits indices and TriMesh

[Hannes Norda]

> Hmm. I think indeed we should support 16 bit indices. Together with double
> support this will lead to 6 different TriMeshBuild functions.
>
> Erwin
>

Yes that would be nice.
There is really no point in having the option to set the triangle stride in
dGeomTriMeshDataBuild() if it always boils down to setting it as 3 * 32
bits.

But of course i respect the fact that the ODE trimesh class is not final, as
stated in the docs.

/Hannes