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-tool.c

@@ -28,7 +28,7 @@
 #include <errno.h>
 
 #include "gio-tool.h"
-
+#include "glib/glib-private.h"
 
 void
 print_error (const gchar *format, ...)
@@ -253,7 +253,7 @@ main (int argc, char **argv)
   const char *command;
   gboolean do_help;
 
-  setlocale (LC_ALL, "");
+  setlocale (LC_ALL, GLIB_DEFAULT_LOCALE);
   textdomain (GETTEXT_PACKAGE);
   bindtextdomain (GETTEXT_PACKAGE, GLIB_LOCALE_DIR);