[ODE] Terrain Collider

[Fabian Herb]

Hello,

I wasn't coding for a long time, now I have returned, and noticed that 
there is another terrain collider from Benoit Chaperot in the contrib 
folder.
The approach of using the existing ray and plane colliders is really 
interesting, I never thought of this. This is of course speeding up 
development enormously.
Now, does anyone need another terrain collider? I myself need a few 
more features, like taking small parts of a larger heightfield, 
different data types etc. So I can either use the ray/plane technique 
in my collider for faster development, or extend Benoit's collider with 
these features. Any suggestions?

Status/features of my collider:
- direct heightfield access
- takes parts of large heightfields, for multiple geoms from one large 
heightfield
- customizable data type (edit in header file)
- extendable for callback approach (to avoid heightfield access)
- selectable triangle layout
- app supplies min/max heightfield values, for faster aabb creation
- geoms can be moved around in space (not rotated)
- sphere collision working with small glitches
- box collision partly working

If anyone wants to give it a try, just tell me.

Fabian