Bump AC_PREREQ to 2.53.
diff --git a/configure.in b/configure.in
index 7f49dcc..8b04c03 100644
--- a/configure.in
+++ b/configure.in
@@ -1,6 +1,6 @@
 dnl Process this file with autoconf 2.0 or later to make a configure script.
 AC_REVISION($Revision$)
-AC_PREREQ(2.50)
+AC_PREREQ(2.53)
 AC_INIT(Include/object.h)
 AC_CONFIG_HEADER(pyconfig.h)