The difficulty is not the example, but setting up org-mode to allow
Python and C++ example that use the local libraries, not those
installed system-wide.
* doc/org/.dir-locals.el: Rename as...
* doc/org/.dir-locals.el.in: ... this, so we can easily define
PYTHONPATH and other environment variables.
* doc/org/init.el.in: Enable C++, and make sure but Python
and C++ use the local libraries.
* doc/org/g++wrap.in, doc/org/tut01.org: New files.
* doc/Makefile.am, configure.ac: Adjust.
* wrap/python/spot.py (to_str): Take a parenth argument.
