[clutter] Add missing include

[Emmanuele Bassi <ebassi src gnome org>]

commit a1c4acf227c0f70d429e2cf49f4fe8351b3e87f8
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Wed Jun 10 12:28:59 2015 +0100

    Add missing include
    
    Some X11-related system header is leaking stdlib.h, so when we disable
    the X11 backend we get a compiler warning for atol().

 clutter/clutter-settings.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/clutter/clutter-settings.c b/clutter/clutter-settings.c
index 0bdfdcb..068914d 100644
--- a/clutter/clutter-settings.c
+++ b/clutter/clutter-settings.c
@@ -34,6 +34,8 @@
 #include "clutter-stage-private.h"
 #include "clutter-private.h"
 
+#include <stdlib.h>
+
 #define DEFAULT_FONT_NAME       "Sans 12"
 
 #define CLUTTER_SETTINGS_CLASS(klass)           (G_TYPE_CHECK_CLASS_CAST ((klass), CLUTTER_TYPE_SETTINGS, 
ClutterSettingsClass))