python*-pth packages into meta-packages which will install the non-pth
packages. Bump PKGREVISIONs on the non-pth versions to propagate the
thread change, but leave the *-pth versions untouched to not affect
existing installations.
Sync all PYTHON_VERSIONS_AFFECTED lines in package Makefiles.
Inspired by FreeBSD "ports".
Fix the PLISTs accordingly.
Also, while at it, remove now obsolete compileall.py calls in post-install
targets and insure that extension.mk is in included before builinlinks of
other Python modules.
Discussed with/ok'ed by drochner@.