SMB client redirector

[Luke Leighton]

based on the idea behind ssh-agent, i just added the first version of an
SMB client redirector to clientgen.c.

the code has the potential to provide SMB client connection management;
credential cacheing etc.

in other words, a user runs an smb-agent daemon, then executes a
management tool to initiate a connection to a remote server, and then runs
smbmount, smbclient, rpcclient, smbsh (smbwrapper) etc and the SMB user
credentials all come not from these commands but from the smb-agent.

actually what happens at the moment is that smb-agent makes the SMB
connection on behalf of the smb client program, and maintains it. the
smb-agent could _also_... hmmm... it could manage keep-alives for you, and
also re-establish dropped connections etc.

hmm!