[PATCH] Add test for bug 29530

[Florian Weimer]

* Andreas Schwab via Libc-alpha:

> +static int
> +do_test (void)
> +{
> +  char buf[1001];
> +
> +  xsetlocale (LC_NUMERIC, "de_DE.UTF-8");
> +
> +  /* This used to crash in group_number.  */
> +  sprintf (buf, "%'1000d", 1000);
> +
> +  return 0;
> +}

Should the test check the expected output?

Thanks,
Florian