support for mknod to windows now in cifs vfs

[Steve French]

Martin Koeppe wrote:

>
> Correct me if I'm wrong, but I didn't find a mount option for 
> linux-cifs to disable the samba unix extension mode. You could imagine 
> a samba server share, on which some cifs clients need unix extensions, 
> and others don't have to use it.

I made it a run time option that applied across all mounts.  Making it a 
mount option might be better, but of course would still hit the same 
confusion that other "smb session" and "tree connection" specific mount 
options would have when you try to map them to multiple mounts to the 
same share or multiple mounts to the same server.

    echo 0 > /proc/fs/cifs/LinuxOptionsEnabled