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.

Include/Python.h

@@ -1,11 +1,11 @@
-#ifndef Py_PYTHON_H
-#define Py_PYTHON_H
+#ifndef Py_PYTHON_H #define Py_PYTHON_H
 /* Since this is a "meta-include" file, no #ifdef __cplusplus / extern "C" { */
 
 /* Include nearly all Python header files */
 
 #include "patchlevel.h"
 #include "pyconfig.h"
+#include "pymacconfig.h"
 
 /* Cyclic gc is always enabled, starting with release 2.3a1.  Supply the
  * old symbol for the benefit of extension modules written before then