s3compat system for running s3 components in s4

[tridge at samba.org]

Hi Andrew,

 > This will, I hope, allow me to develop a Samba3 auth module that will
 > ask Samba4 to complete the authentication.  (Removing the need for a
 > passdb.tdb). 

That would be really nice. With that and the named pipe abstraction
that metze has been working on we should be able to offer the s3
fileserver backend as a viable option for s4 users.

I'd eventually like to make this per-share, but doing it for all file
services will work in the short term.

It should also allow the s3 printing code to work in s4, which would
be a nice bonus. All the VFS modules should also work. It will need a
lot of testing, but I think at least the principle is sound.

Cheers, Tridge