[devhelp] build: Fix broken autoconf prerequisite

[Colin Walters <walters src gnome org>]

commit 02927413383f13b7fcc55e54b8f34c08958c507f
Author: Colin Walters <walters verbum org>
Date:   Mon Apr 13 14:47:16 2015 -0400

    build: Fix broken autoconf prerequisite
    
    I'm sure this was a typo.

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 7db7e0b..6934a69 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,4 +1,4 @@
-AC_PREREQ([3.64])
+AC_PREREQ([2.64])
 AC_INIT([Devhelp],
         [3.16.2],
         [http://bugzilla.gnome.org/enter_bug.cgi?product=devhelp],