Revert "GIOSchedulerJob: Improve struct packing"

This reverts commit a2094d5e56.

https://bugzilla.gnome.org/show_bug.cgi?id=616754

gio/gioscheduler.c

@@ -51,10 +51,11 @@ struct _GIOSchedulerJob {
   GSourceFunc cancel_func; /* Runs under job map lock */
   gpointer data;
   GDestroyNotify destroy_notify;
+
+  gint io_priority;
   GCancellable *cancellable;
   GMainContext *context;
 
-  gint io_priority;
   guint idle_tag;
 };