[ODE] inconsistency between dGeomDestroy and dBodyDestroy

[Chris Ledwith]

Hi,
I noticed that dGeomDestroy does nothing but call delete on the geom, 
and the geom's destructor calls dSpaceRemove to remove itself from its 
parent space, whereas dBodyDestroy does this sort of management work to 
remove itself from the world, and the body uses a default destructor. 
Also, perhaps dGeomDestroy should manage removing the geom from its 
owner body's list, much like how dBodyDestroy manages the removal of the 
body's geoms' references to itself.

-C