Clean up Python embedding to build on zizzer (where python2.4

Clean up Python embedding to build on zizzer (where python2.4
is currently in /usr/local instead of /usr).

SConstruct:
    Use information from the Python interpreter used to run scons
    to find the version & paths for include & library files.
    This means that linking with a different interpreter requires
    invoking scons with that interpreter... add comment to that effect.
src/sim/main.cc:
    Check return codes of Python interpreter calls for errors.
    Get rid of include of obsolete header.

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extra : convert_revision : 90916bd8690fe1e6c9afdb0dfa1aa0d352a73a46