This fixes configure issues with recent autoconf, e.g:
  autoreconf: Entering directory `Modules/_ctypes/libffi'
  autoreconf: configure.ac: not using Gettext
  autoreconf: running: aclocal --force
  configure.ac:26: error: m4_copy: won't overwrite defined macro: _AC_ARG_VAR_PRECIOUS
  configure.ac:26: the top level

The problem is still present in python-2.6.5 but fixed in python-svn.

Index: Python-2.7.1/Modules/_ctypes/libffi/Makefile.am
===================================================================
--- Python-2.7.1.orig/Modules/_ctypes/libffi/Makefile.am	2010-03-19 14:59:20.000000000 -0400
+++ Python-2.7.1/Modules/_ctypes/libffi/Makefile.am	2010-12-26 10:05:56.112625174 -0500
@@ -2,7 +2,7 @@
 
 AUTOMAKE_OPTIONS = foreign subdir-objects
 
-SUBDIRS = include testsuite man
+SUBDIRS = include
 
 EXTRA_DIST = LICENSE ChangeLog.v1 ChangeLog.libgcj configure.host \
 	src/alpha/ffi.c src/alpha/osf.S src/alpha/ffitarget.h \
@@ -34,8 +34,6 @@
 	libtool-version ChangeLog.libffi m4/libtool.m4 \
 	m4/lt~obsolete.m4 m4/ltoptions.m4 m4/ltsugar.m4 m4/ltversion.m4
 
-info_TEXINFOS = doc/libffi.texi
-
 ## ################################################################
 
 ##
Index: Python-2.7.1/Modules/_ctypes/libffi/configure.ac
===================================================================
--- Python-2.7.1.orig/Modules/_ctypes/libffi/configure.ac	2010-12-26 10:06:09.752605599 -0500
+++ Python-2.7.1/Modules/_ctypes/libffi/configure.ac	2010-12-26 10:07:18.260769612 -0500
@@ -409,7 +409,7 @@
 
 AC_CONFIG_LINKS(include/ffitarget.h:src/$TARGETDIR/ffitarget.h)
 
-AC_CONFIG_FILES(include/Makefile include/ffi.h Makefile testsuite/Makefile man/Makefile libffi.pc)
+AC_CONFIG_FILES(include/Makefile include/ffi.h Makefile testsuite/Makefile man/Makefile libffi.pc Makefile)
 
 AC_CONFIG_LINKS(include/ffi_common.h:include/ffi_common.h)