[gnome-settings-daemon] Fix build on non-Linux platforms

[Emilio Pozuelo Monfort <epm src gnome org>]

commit ce86f098c1d4608a8cf5aa24f2f2213346421cad
Author: Emilio Pozuelo Monfort <pochu27 gmail com>
Date:   Sun Mar 24 21:38:17 2013 +0100

    Fix build on non-Linux platforms
    
    We need stdlib.h to get the definition of NULL.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=696515

 plugins/power/gsd-backlight-linux.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/plugins/power/gsd-backlight-linux.c b/plugins/power/gsd-backlight-linux.c
index f8f91a0..bbaf490 100644
--- a/plugins/power/gsd-backlight-linux.c
+++ b/plugins/power/gsd-backlight-linux.c
@@ -19,6 +19,8 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#include <stdlib.h>
+
 #include "config.h"
 
 #include "gsd-backlight-linux.h"