[planner] Bump GTK dependency to 2.24.

[Luis Menina <lmenina src gnome org>]

commit 8f75baad7a588e48cfd173030f6a1ac9ef788555
Author: Luis Menina <liberforce freeside fr>
Date:   Wed Mar 6 00:34:46 2013 +0100

    Bump GTK dependency to 2.24.
    
    It's been out for 2 years and is the version closest to GTK 3
    compatibility.

 README       |    2 +-
 configure.ac |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/README b/README
index b2489ef..0b3da0c 100644
--- a/README
+++ b/README
@@ -57,7 +57,7 @@ Installation
 Dependencies:
 
 GLIB 2.6.0
-GTK 2.14.0
+GTK 2.24.0
 LIBGNOMECANVAS 2.10.0
 LIBGLADE 2.3.0
 GNOME_VFS 2.10.0
diff --git a/configure.ac b/configure.ac
index 7a786cb..77127c3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -65,7 +65,7 @@ dnl If you add a version number here, you *must* add an AC_SUBST line for
 dnl it too, or it will never make it into the spec file!
 
 GLIB_REQUIRED=2.6.0
-GTK_REQUIRED=2.18.0
+GTK_REQUIRED=2.24.0
 LIBGNOMECANVAS_REQUIRED=2.10.0
 LIBGLADE_REQUIRED=2.3.0
 GNOME_VFS_REQUIRED=2.10.0