This patch adds an --enable-universalsdk flag to configure. When this is 
used on a MacOS X system with Xcode 2.1 or later this can be used to 
create universal (aka "fat") binaries for python and its extensions.

This patches updates configure.in, which means autoconf should be used 
before checking in the patch.

I've tested the patch on Linux as well, it seems to have no bad effects 
there.

This patch is a cleaned up version of the code behind the --enable-
universal-sdk flag in the python24-fat tree at http://svn.pythonmac.org/
python24/python24-fat.