'--help-commands' option).
Shuffled imports around in a few command modules to avoid expensive
up-front import of sysconfig (and resulting delays in generating list
of all commands).
Tweaked some help strings to be consistent with documentation.
Don't call 'set_final_options()' in 'run()' anymore -- that's now
guaranteed to be taken care of for us by the Distribution instance.
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.
