[ODE] configure improvements

[Bram Stolk]

Rodrigo Hernandez wrote:
> Oh no no no no no no, you do not want to install anything that has to do 
> with examples or drawstuff, they are for internal testing of the library 
> only, and as examples on how to get something going, we dont want people 
> using drawstuff outside ode, and we dont want to trash their hard drives 
> with example executables, with this perspective in mind, the build 
> process is not broken at all, just cd into ode/ode/tests and call your 
> example from there ( cd ode/ode/tests ; path/to/build/test_boxstack).

Yes, I already use this method.
But you're right, we can leave it like this.

   Bram