added support for the provides, requires, and obsoletes metadata fields

This support was only a first cut, and doesn't deserve to be in
a released version (where we have to support it in an ongoing
manner)

requires and provides. requires is a sequence of strings, of the
form 'packagename-version'. The dependency checking so far merely
does an '__import__(packagename)' and checks for packagename.__version__
You can also leave off the version, and any version of the package
will be installed.
There's a special case for the package 'python' - sys.version_info
is used, so
requires= ( 'python-2.3', )
just works.

Provides is of the same format as requires - but if it's not supplied,
a provides is generated by adding the version to each entry in packages,
or modules if packages isn't there.
Provides is currently only used in the PKG-INFO file. Shortly, PyPI
will grow the ability to accept these lines, and register will be
updated to send them.

There's a new command 'checkdep' command that runs these checks.
For this version, only greater-than-or-equal checking is done. We'll
add the ability to specify an optional operator later.

From SF patch #852334.

   have two tuples listing the legal keywords for setup() and Extension()

    suggested by PEP 291.

  Fixed by catching all exceptions that are subclasses of DistutilsError,
  so only the error message will be printed.  You can still get the
  whole traceback by enabling the Distutils debugging mode.

See http://mail.python.org/pipermail/distutils-sig/2002-November/003039.html

   whether the Distutils being used supports a particularly capability.

   (This idea was originally suggested by Juergen Hermann as a method
    on the Distribution class.  I think it makes more sense as a
    function in core.py, and that's what this patch implements.)

Note that distutils.core.DEBUG still works if client code uses it, but
the core code avoids circular references by using distutils.debug.

Fixes a bug for Solaris pkgtool (bdist_pkgtool) that would have
prevented it from building subpackages.

This is a conservative version of SF patch 504889.  It uses the log
module instead of calling print in various places, and it ignores the
verbose argument passed to many functions and set as an attribute on
some objects.  Instead, it uses the verbosity set on the logger via
the command line.

The log module is now preferred over announce() and warn() methods
that exist only for backwards compatibility.

XXX This checkin changes a lot of modules that have no test suite and
aren't exercised by the Python build process.  It will need
substantial testing.

fairly tight control, and the '_setup_stop_after' and '_setup_distribution'
globals to provide the tight control.

This isn't entirely reliable yet: it dies horribly with a NameError on the
example PIL setup script in examples/pil_setup.py (at least with Python
1.5.2; untested with current Python).  There's some strangeness going
on with execfile(), but I don't understand it and don't have time
to track it down right now.

Changed 'core.setup()' so it sets them to reasonable defaults.
Tweaked how the "usage" string is generated: 'core' now provides
  'gen_usage()', which is used instead of 'USAGE'.
Modified "build_py" and "sdist" commands to refer to
  'self.distribution.script_name' rather than 'sys.argv[0]'.

muddling through IOError and OSError exception objects right here.

do so if DEBUG is true.

"from distutils.core import" it.

Changed the exception-handling code in 'setup()' to re-raise exceptions
  if DEBUG is true.

dump the Distribution's 'command_options' dict after parsing config files,
and then after parsing the command line.

Tweaked error-generating code.

exceptions better.

errors in the setup script or on the command line, so shouldn't result
in a traceback.

the Command class from core.py to cmd.py.  No other code needs changing
though; distutils.core still provides the Command and Distribution classes,
although indirectly now.

Simplified 'Command.get_peer_option()' a tad -- just call 'find_peer()'
  to get the peer command object.
Updated 'Command.copy_file()' to take a 'link' parameter, just like
  'util.copy_file()' does now.
Added 'Command.make_archive()' to wrap 'util.make_archive()'.

'has_ext_modules()', 'has_c_libraries()', 'has_modules()', and 'is_pure()'.

handle OSError and DistutilsExecError now.