python tests: support PEP-3147 installation layout This fixes several spurious testsuite failures with python >= 3.2, introduced by recent commit v1.12.4-43-ge0e99ed, "python: improve support for modern python (CPython 3.2 and PyPy)". * t/ax/am-test-lib.sh (python_has_pep3147, pyc_location, py_installed): New functions. ($am_pep3147_tag): New variable. * t/py-compile-basic2.sh: Deleted, too difficult to adapt for the gain it would offer; move the still relevant parts ... * t/py-compile-basic.sh: ... here. Adapt and adjust the rest of the test as well. * t/nobase-python.sh: Adapt and adjust. * t/py-compile-basedir.sh: Likewise. * t/py-compile-destdir.sh: Likewise. * t/py-compile-option-terminate.sh: Likewise. * t/python-pr10995.sh: Likewise. * t/python-virtualenv.sh: Likewise. * t/python10.sh: Likewise. * t/python12.sh: Likewise. * t/python3.sh: Likewise. * t/list-of-tests.mk: Adjust list of tests. Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>