Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Now pam_nologin(8) will provide an account management function
instead of an authentication function. There are a design reason
and a practical reason for that. First, the module belongs in
account management because it checks availability of the account
and does no authentication. Second, there are existing and potential
PAM consumers that skip PAM authentication for good or for bad.
E.g., sshd(8) just prefers internal routines for public key auth;
OTOH, cron(8) and atrun(8) do implicit authentication when running
a job on behalf of its owner, so their inability to use PAM auth
is fundamental, but they can benefit from PAM account management.

Document this change in the manpage.

Modify /etc/pam.d files accordingly, so that pam_nologin.so is listed
under the "account" function class.

Bump __FreeBSD_version (mostly for ports, as this change should be
invisible to C code outside pam_nologin.)

PR: bin/112574
Approved by: des, re

Major cleanup & homogenization.

Don't list pam_unix in the session chain, since it does not provide any
session management services.

Sponsored by: DARPA, NAI Labs

Use pam_rhosts(8).

Awright, egg on my face. I should have taken more time with this. The
conversion script generated the wrong format, so the configuration files
didn't actually work. Good thing I hadn't thrown the switch yet...

Sponsored by: DARPA, NAI Labs (but the f***ups are all mine)

pam.d-style configuration, auto-generated from pam.conf.

Sponsored by: DARPA, NAI Labs