[ODE] Triangle-box collider contribution

[Adam D. Moss]

Thanks for supplying capsule-vs-tri code, Alen.  More comments
below.

Alen Ladavac wrote:
>>I don't know whether it makes sense for ODE to
>>ever promote cylinders to a core primitive though).
> 
> Why not? They are a necessity if you want to model barrels and cans, because
> they can both stand upwards and roll. Useful for wheels as well, if you can
> afford it - spheres are fast but very poor aproximation for wheels.

My main and perpetual source of hesitation is that introducing /any/
new core geom is not a decision to made lightly, because every time
a new core geom is introduced, the introduction of any /future/ geoms
becomes increasingly costly in terms of effort and footprint (assuming
that the matrix of supported obj-vs-obj colliders should have no
unimplemented meaningful cases, which IMO is a prerequisite for
core geoms).

However, personally I'd be happy to promote to core an everything-vs-
cylinder implementation which seemed solid and had interested parties
to keep it from rusting too badly.  (Russ, if you have an opinion
either way then please speak up :)).

After this, I can only think of two or three more geoms which seem
sane and generally-useful, such as heightmaps and general convex hulls.
In the future perhaps we'll extend to madness such as colliding
parametric and time-extruded surfaces, where there's a call for it
and someone has the code, but for now ODE's colliders seem to be
shaping up pretty well.  Thanks to all contributors!

--Adam
-- 
Adam D. Moss   . ,,^^   adam at gimp.org   http://www.foxbox.org/   co:3