python: improve support for modern python (CPython 3.2 and PyPy)
This fixes automake bug#8847.
* m4/python.m4 (AM_PATH_PYTHON): Add python3.3 to
_AM_PYTHON_INTERPRETER_LIST.
* lib/py-compile: Fix compiled filenames for PEP-3147, currently
implemented in CPython 3.2 and newer. Do not create '.pyo' files
for PyPy.