Require autoconf 2.59 instead of 2.61.

git-svn-id: svn://bind10.isc.org/svn/bind10/branches/f2f200910@295 e5f2f494-b856-4b98-b285-d166d9295462

configure.ac

@@ -1,7 +1,7 @@
 #                                               -*- Autoconf -*-
 # Process this file with autoconf to produce a configure script.
 
-AC_PREREQ([2.61])
+AC_PREREQ([2.59])
 AC_INIT(bind, 10.0.0, bind10-bugs@isc.org)
 AC_CONFIG_SRCDIR(README)
 AM_INIT_AUTOMAKE