[ODE] configure improvements

[Rodrigo Hernandez]

Using the config script would require ODE to be already installed, so we 
get a catch 22 situation.
Instead we could define the string on config.h and leave 
"../../drawstuff/textures" as default when no config.h is provided.

Bram Stolk wrote:

>To really clean up the autoconf/automake interface, we could
>opt for the approach used in the plib project:
>seperate configure.in files for the lib, and the examples.
>
>If we went this route, we could do it properly, using sutff
>like:
>
>CXXFLAGS = `ode-config --cflags`
>
>'make install' creates a file $prefix/bin/ode-config which
>should be used by applications using ode. It's much like
>fltk-config mechanism.
>Currently, this mechanism is unused in ode.
>We should consider using it.
>
>  
>