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

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

Load the ECDSA key if there is one.

MFC after: 1 week

Do not use passphraseless keys for authentication unless the nullok
option was specified.

PR: bin/81231
Submitted by: "Daniel O'Connor" <doconnor@gsoft.com.au>
MFC after: 3 days

Mechanically kill hard sentence breaks.

mdoc(7) police: markup laundry.

Complete rewrite of pam_ssh(8). The previous version was becoming hard
to maintain, and had security issues which would have required a major
rewrite to address anyway.

This implementation currently starts a separate agent for each session
instead of connecting each new session to the agent started by the first
one. While this would be a Good Thing (and the old pam_ssh(8) tried to
do it), it's hard to get right. I'll revisit this issue when I've had a
chance to test some modifications to ssh-agent(1).

mdoc(7) police: removed gratuitous .Pp call.

Merge in most non-style differences from Andrew Korty's pam_ssh 1.7.

NAI DBA update.

mdoc(7) police: fix one pam_unix(8) left-over, sort xrefs.

Create a pam_ssh(8) man page, based on a repo-copy of pam_unix(8).
License modified with original author's permission.

Sponsored by: DARPA, NAI Labs

Big module makeover; improve logging, standardise variable names,
introduce ability to change passwords for both "usual" Unix methods
and NIS.

Fix a couple of cross-references to reflect the reality of the module.

mdoc(7) police: -xwidth has been fold into -width.

mdoc(7) police: fixed markup, a little bit.

Clean up (and in some cases write) the PAM mudules, using
o The new options-processing API
o The new DEBUG-logging API

Add man(1) pages for ALL modules. MDOC-Police welcome
to check this.

Audit, clean up while I'm here.