Make source compilable via GNU autotools which are part of RHEL 5.
git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@3676 3789f03b-4d11-0410-bbf8-ca57d06f2519
diff --git a/common/zlib/configure.ac b/common/zlib/configure.ac
index 2befc77..532012a 100644
--- a/common/zlib/configure.ac
+++ b/common/zlib/configure.ac
@@ -1,7 +1,7 @@
# -*- Autoconf -*-
# Process this file with autoconf to produce a configure script.
-AC_PREREQ([2.61])
+AC_PREREQ([2.57])
AC_INIT([zlib], [1.1.4])
AM_INIT_AUTOMAKE([-Wall foreign dist-bzip2])