cool! a unix socket smb redirector. code based on smbfilter and

cool!  a unix socket smb redirector.  code based on smbfilter and
ideas from ssh-agent.

the intent is to be able to share smb sessions using cli_net_use_add()
across multiple processes, where one process knows the target server
name, user name and domain, but not the smb password.
(This used to be commit 294b653f2e9cdc1864ec638ae8b4300df25723cf)