[ODE] ccylinder-box collision implemented

[Russ Smith]

hi,

capped-cylinder-to-box collision has been (finally) implemented. you can
see it in action in the boxstack demo. there are a few points to note:

  * a maximum of one contact point is generated between any cylinder and
    box, although sometimes two would be better for increased stability.
    thus when a cylinder is lying flat on top of a box it will jitter a
    bit. this is the same problem that afflicts box-box contact. both of
    these problem will be solved later (i.e. we'll eventually have the
    complete set of contacts generated).

  * with deep cylinder-box penetration (e.g. the cylinder pushed fully
    into the box), the contact normal is not set in the most desirable
    way to reduce penetration the fastest - instead the system might
    take "the long way out". this should not be much of a problem in
    practice. this will also be fixed later.

now all collision cases in ODE's default collision are implemented -
although box-box and box-cylinder need code for extra contact
generation.

enjoy!

russ.

--
Russell Smith
http://www.q12.org