[ODE] Pushing through collisions

[Nguyen Binh]

Hi Alen,

AL> 5) The cylinder-sphere combination in our collider. Nguyen, I belive that we
AL> have found a case where contact normal is NAN if sphere center is on the
AL> cylinder axis. I'll send you a fix when we have time to do it.

    Possibly not! The small sphere will be stuck in the center of
    large cylinder when its center is deep inside: i.e sphere's center
    is between cylinder high-base and low-base. In this case, your
    code assumes that it's a side penetration, but it's actually a
    very deep bottom penetration.

    For the case sphere center is on the cylinder axis, I didn't
    notice it. I had successful made a large stable stack of cylinders and
    spheres. And I'm sure all sphere center is in cylinders axis.

    Nguyen Binh.

    I'm very very interested in another iterative solvers but
    I'll finish porting Croteam's cylinder-vs anything to ODE before
    reading more about it. Before, I had tried but without any
    success :( . So please keep your iterative solver progress
    updated. :)