[gthumb] include stdlib for atoi

[Paolo Bacchilega <paobac src gnome org>]

commit 1571c5457171c58dd10b75cb3b025317582c343d
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Sun Mar 8 12:19:49 2020 +0100

    include stdlib for atoi

 gthumb/gth-file-data.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/gthumb/gth-file-data.c b/gthumb/gth-file-data.c
index b60aab3b..27d30bc0 100644
--- a/gthumb/gth-file-data.c
+++ b/gthumb/gth-file-data.c
@@ -21,6 +21,7 @@
 
 #include <config.h>
 #include <string.h>
+#include <stdlib.h>
 #include "glib-utils.h"
 #include "gth-duplicable.h"
 #include "gth-metadata.h"