[PATCH,HURD] implement syncfs

[Roland McGrath]

> > +/* Make all changes done to all files on the file system associated
> > +   with FD actually appear on disk.  */
> > +int
> > +syncfs (int fd)
> > +{
> > +  /* This is not actually synchronous; we don't wait.  */
> > +  error_t err = HURD_DPORT_USE (fd, __file_syncfs (port, 0, 0));
> 
> Note that syncfs in Linux actually does wait for completion of the writeback,
> that's the whole point of the syscall.

In that case args should be 1, 0.