[ODE] Velocity at relative point

[Chris Ledwith]

> It might be a good idea to add a function like this to next ODE version?
>
> const dReal * dBodyGetRelLinearVel  (dBodyID,
>               dReal px, dReal py, dReal pz);
>

ODE already has such a function, it's called dBodyGetRelPointVel.

-C