[linux-cifs-client] special files on Services for Unix (SFU)

[Steve French]

This is interesting information - I should be able to verify it easily
enough.

Now the next interesting question is whether to do this (ie create and
recognize such special files) only when
1) Unix exensions are not negotiated
and
2) a new mount option (for which we need a name) is specified

or whether 1) is sufficient (ie this is done automatically)

I would have prefer this information being in EAs rather than in file
data, but there are cases where file data is the only choice.  The other
interesting problem is that the Mac client uses a magic file size and
format for symlinks (which is different from the internix one).