hurd: Fix standard compliance of some statvfs fields

Standards require that the f_bsize, f_frsize, f_flag and f_namemax fields be
unsigned long.  They used to be only unsigned on hurd, which happens to be
compatible with unsigned long on the only existing, 32bit, port.  We can
thus merely fix the type.

	* sysdeps/mach/hurd/bits/statvfs.h (struct statvfs): Make f_bsize,
	f_namemax, f_frsize, and f_flag fields unsigned long int instead of
	unsigned int.
	(struct statvfs64): Likewise.