[gtk] tests/frame-stats.c: Include stdlib.h

[Chun-wei Fan <fanchunwei src gnome org>]

commit 6ec546be02079b5ff3f5bdb034c119a635362b9a
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Tue Feb 11 20:46:19 2020 +0800

    tests/frame-stats.c: Include stdlib.h
    
    It is used for exit().

 tests/frame-stats.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/tests/frame-stats.c b/tests/frame-stats.c
index 289a70c6b7..a9fb004072 100644
--- a/tests/frame-stats.c
+++ b/tests/frame-stats.c
@@ -1,6 +1,7 @@
 /* -*- mode: C; c-basic-offset: 2; indent-tabs-mode: nil; -*- */
 
 #include <gtk/gtk.h>
+#include <stdlib.h>
 
 #include "frame-stats.h"
 #include "variable.h"