is now obsolete), and changed the default path calculations.
$PYTHONPATH is now added as a prefix (like it's always been on Unix);
$PYTHONHOME takes precedence over the program pathname; and only one
landmark is needed.
lives to the end of the path.
(Still to do: add $PYTHONPATH to the front instead of using it as is;
add the Win32 registry paths as in getpath_nt.c (which can then
retire).)