'install_site_lib' and install_site_platlib' on non-POSIX platforms.
Should at least work for NT, as this is adopted from Amos Latteier's NT
patches. Also added extensive comments bitching about the inadequacy of
the current model, both under POSIX and NT (and probably other) systems.
of the 'install_py' command rather than 'build_py'. Obviously, this
meant that the 'build_py' and 'install_py' modules had to change; less
obviously, so did 'install' and 'build', since these higher-level
commands must make options available to control the lower-level
commands, and some compilation-related options had to migrate with the
code.
