MacOS X: Enable 4-way universal builds

This patch adds a new configure argument on OSX:
        --with-universal-archs=[32-bit|64-bit|all]

When used with the --enable-universalsdk option this controls which
CPU architectures are includes in the framework. The default is 32-bit,
meaning i386 and ppc. The most useful alternative is 'all', which includes
all 4 CPU architectures supported by MacOS X (i386, ppc, x86_64 and ppc64).

This includes limited support for the Carbon bindings in 64-bit mode as well,
limited because (a) I haven't done extensive testing and (b) a large portion
of the Carbon API's aren't available in 64-bit mode anyway.

I've also duplicated a feature of Apple's build of python: setting the
environment variable 'ARCHFLAGS' controls the '-arch' flags used for building
extensions using distutils.
diff --git a/Lib/distutils/sysconfig.py b/Lib/distutils/sysconfig.py
index 27a770b..9993fba 100644
--- a/Lib/distutils/sysconfig.py
+++ b/Lib/distutils/sysconfig.py
@@ -539,6 +539,26 @@
                     flags = re.sub('-isysroot [^ \t]*', ' ', flags)
                     _config_vars[key] = flags
 
+            else:
+
+                # Allow the user to override the architecture flags using
+                # an environment variable.
+                # NOTE: This name was introduced by Apple in OSX 10.5 and
+                # is used by several scripting languages distributed with
+                # that OS release.
+
+                if 'ARCHFLAGS' in os.environ:
+                    arch = os.environ['ARCHFLAGS']
+                    for key in ('LDFLAGS', 'BASECFLAGS',
+                        # a number of derived variables. These need to be
+                        # patched up as well.
+                        'CFLAGS', 'PY_CFLAGS', 'BLDSHARED'):
+
+                        flags = _config_vars[key]
+                        flags = re.sub('-arch\s+\w+\s', ' ', flags)
+                        flags = flags + ' ' + arch
+                        _config_vars[key] = flags
+
     if args:
         vals = []
         for name in args: