[gtk+] Bump atk dep

[Matthias Clasen <matthiasc src gnome org>]

commit d58c750db5085a6e7ffe3490acc938a0694743d4
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Oct 28 08:08:49 2014 -0400

    Bump atk dep
    
    Needed for ATK_STATE_HAS_TOOLTIP.

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 5cac154..7c78d52 100644
--- a/configure.ac
+++ b/configure.ac
@@ -43,7 +43,7 @@ m4_define([gtk_binary_version], [3.0.0])
 # required versions of other packages
 m4_define([glib_required_version], [2.43.0])
 m4_define([pango_required_version], [1.36.7])
-m4_define([atk_required_version], [2.12.0])
+m4_define([atk_required_version], [2.15.1])
 m4_define([cairo_required_version], [1.12.0])
 m4_define([gdk_pixbuf_required_version], [2.30.0])
 m4_define([introspection_required_version], [1.39.0])