[ODE] odecpp.h

[Henry]

Been changing my code to use the new cpp header and have noticed a 
couple of things.

1. It's possible to create a dSpace object which leaves the system in an 
inconsistent state.

   dSpace ()
     { _id = 0; }

That is dSpace can't be used anywhere and can't be deleted without 
causing a seg fault. It is required as it's a base for simpleSpace and 
hashSpace so why not make it pure virtual or make the constructor 
private.

2. A few functions take d*ID as parameters rather than objects. eg...

   void add (dGeomID x)
     { dSpaceAdd (_id, x); }

It feels a bit nicer to me to do this...


   void add (dGeom x)
     { dSpaceAdd (_id, x->id()); }

What do you think?


Henry