Winbind updates!

Winbind updates!

This updates the 'winbind' authentication module and winbind's 'PAM' (actually
netlogon) code to allow smbd to cache connections to the DC.

This is particulary relevent when we need mutex locks already - there is no
parallelism to be gained anyway.

The winbind code authenticates the user, and if successful, passes back the
'info3' struct describing the user.  smbd then interprets that in exactly the
same way as an 'ntdomain' logon.

Also, add parinoia to winbind about null termination.

Andrew Bartlett
(This used to be commit 167f122b670d4ef67d78e6f79a2bae3f6e8d67df)