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/unix/configure.ac b/unix/configure.ac
index 058218d..dd2b633 100644
--- a/unix/configure.ac
+++ b/unix/configure.ac
@@ -1,5 +1,5 @@
dnl Process this file with autoconf to produce a configure script.
-AC_PREREQ([2.61])
+AC_PREREQ([2.57])
AC_INIT([tigervnc], [0.0.90], [http://www.tigervnc.org])
AM_INIT_AUTOMAKE([-Wall foreign dist-bzip2])