gio tools: Use the proper string for default locale for setlocale()

This makes use of the string we now have from glib-private.h in the
last commit so that setlocale() sets the default system locale
correctly and therefore show the translated messages properly.

Fixes issue #1169.

gio/gio-querymodules.c

@@ -26,6 +26,8 @@
 #include <errno.h>
 #include <locale.h>
 
+#include "glib/glib-private.h"
+
 static gboolean
 is_valid_module_name (const gchar *basename)
 {
@@ -160,7 +162,7 @@ main (gint   argc,
       return 1;
     }
 
-  setlocale (LC_ALL, "");
+  setlocale (LC_ALL, GLIB_DEFAULT_LOCALE);
 
   /* Be defensive and ensure we're linked to GObject */
   g_type_ensure (G_TYPE_OBJECT);