s3-auth: Add passwd_to_SamInfo3().

s3-auth: Add passwd_to_SamInfo3().

First this function tries to contacts winbind if the user is a domain
user to get valid information about it. If winbind isn't running it will
try to create everything from the passwd struct. This is not always
reliable but works in most cases. It improves the current situation
which doesn't talk to winbind at all.

Pair-Programmed-With: Guenther Deschner <gd@samba.org>
Signed-off-by: Guenther Deschner <gd@samba.org>
Signed-off-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>