This should help avoiding issues like #13170.

Because of implicit relative imports, _backport.tarfile already imported
shutil from the backports instead of the stdlib; I have inlined the only
function it needed to remove the circular dependency between these
modules.

This method was named reinitialize_command in distutils and accompanied
by a comment suggesting to change it to get_reinitialized_command.
Following that, I did the change for distutils2, but it proved
confusing: The Distribution object has an internal cache of command
objects, to make sure only one instance is ever used, and the name
get_reinitialized_command could suggest that the object returned was
independent of that cache, which it was not.  I?m reverting the name
change to make code clearer.

There was already a test for this, but it was complicated and had a
subtle bug (custom command objects need to be put in dist.command_obj so
that other command objects may see them) that rendered it moot.

d2 uses the shutil.make_archive function (moved from distutils),
which does not support compress.  There is no test to check that
?bdist --format whatever? works, so this slipped by.

Backports:
- sysconfig is now always imported from our backports
- when hashlib is not found, our backport is used instead of the md5
  module (debatable; we could just drop hashlib)

Version-dependent features:
- PEP 370 features are only enabled for 2.6+
- the check for sys.dont_write_bytecode was fixed to use getattr
  with a default value instead of hasattr

Idioms/syntax:
- octal literals lost their extra 0
- misused try/except blocks have been changed back to try/finally
  (it?s legal in 2.4 too, it?s only try/except/finally that isn?t)
- exception catching uses the regular 2.x idiom instead of sys.exc_info
- file objects are closed within finally blocks (this causes much
  whitespace changes but actually makes diff with packaging easier)

Renamed modules:
- some missed renamings (_thread, Queue, isAlive, urllib.urlsplit, etc.)
  were fixed

Other:
- a few false positive replacements of ?packaging? by ?distutils2? in
  comments or docstrings were reverted
- util.is_packaging regained its name
- assorted whitespace/comment/import changes to match packaging

Logging calls have the signature (msg, *args, **kwargs) so that the
%-formatting can be delayed until it is needed.  Logger objects also have an
isEnabledFor method that can be used to isolate expensive code.

Next steps: use only one of d2.logger methods or logging module functions;
use a proper handler in our test machinery instead of monkey-patching; remove
cmd.warn and cmd.announce and use logging instead.  TODOs have been added in
the modules and on the wiki.