[ODE] Pushing through collisions

[Alen Ladavac]

From: "Nguyen Binh" <ngbinh at glassegg.com>
>     First, it is not always true when the center is pushed deep inside
>     cylinder then the side is closer. Imagine when you have a flat
>     cylinder with small size but large radius.

You are correct, the choice of separating axis is wrong if the sphere center
is inside the cylinder.

>     Second,maybe I got the Nan thing you stated before. The depth
>     normal is just switch right and left so the small sphere is stuck
>     there.

The Nan problem is only an additional issue, but should be hard to fix
either. It is just a matter of normalizing a zero vector.

We will have that both corrected in a few days, and I'll send you a new
version. But I believe that you can also make the changes yourself, as it is
only a matter of testing distance between top/bottom and side, if sphere
center is inside, and some >epsilon testing for the Nan.

Thanks for pointing this one out,
Alen