[gnome-control-center] configure: Bump gtk+ version requirement

[Rui Matos <rtcm src gnome org>]

commit cf4d682df66038729b011bb08efbd92b1a5494de
Author: Rui Matos <tiagomatos gmail com>
Date:   Thu Dec 4 15:26:39 2014 +0100

    configure: Bump gtk+ version requirement
    
    Needed for gtk_label_get/set_xalign() .

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index e98b347..27dbaef 100644
--- a/configure.ac
+++ b/configure.ac
@@ -86,7 +86,7 @@ dnl Check that we meet the  dependencies
 dnl ==============================================
 
 GLIB_REQUIRED_VERSION=2.39.91
-GTK_REQUIRED_VERSION=3.13.0
+GTK_REQUIRED_VERSION=3.15.0
 PA_REQUIRED_VERSION=2.0
 CANBERRA_REQUIRED_VERSION=0.13
 GDKPIXBUF_REQUIRED_VERSION=2.23.0