ssh: update to OpenSSH 9.1p1

Release notes are available at https://www.openssh.com/txt/release-9.1

9.1 contains fixes for three minor memory safety problems; these have
lready been merged to the copy of OpenSSH 9.0 that is in the FreeBSD base
system.

Some highlights copied from the release notes:

Potentially-incompatible changes
--------------------------------

* ssh(1), sshd(8): SetEnv directives in ssh_config and sshd_config
are now first-match-wins to match other directives. Previously
if an environment variable was multiply specified the last set
value would have been used. bz3438

* ssh-keygen(8): ssh-keygen -A (generate all default host key types)
will no longer generate DSA keys, as these are insecure and have
not been used by default for some years.

New features
------------

* ssh(1), sshd(8): add a RequiredRSASize directive to set a minimum
RSA key length. Keys below this length will be ignored for user
authentication and for host authentication in sshd(8).

* sftp-server(8): add a "users-groups-by-id@openssh.com" extension
request that allows the client to obtain user/group names that
correspond to a set of uids/gids.

* sftp(1): use "users-groups-by-id@openssh.com" sftp-server
extension (when available) to fill in user/group names for
directory listings.

* sftp-server(8): support the "home-directory" extension request
defined in draft-ietf-secsh-filexfer-extensions-00. This overlaps
a bit with the existing "expand-path@openssh.com", but some other
clients support it.

* ssh-keygen(1), sshd(8): allow certificate validity intervals,
sshsig verification times and authorized_keys expiry-time options
to accept dates in the UTC time zone in addition to the default
of interpreting them in the system time zone. YYYYMMDD and
YYMMDDHHMM[SS] dates/times will be interpreted as UTC if suffixed
with a 'Z' character.

Also allow certificate validity intervals to be specified in raw
seconds-since-epoch as hex value, e.g. -V 0x1234:0x4567890. This
is intended for use by regress tests and other tools that call
ssh-keygen as part of a CA workflow. bz3468

* sftp(1): allow arguments to the sftp -D option, e.g. sftp -D
"/usr/libexec/sftp-server -el debug3"

* ssh-keygen(1): allow the existing -U (use agent) flag to work
with "-Y sign" operations, where it will be interpreted to require
that the private keys is hosted in an agent; bz3429

MFC after: 2 weeks
Relnotes: Yes
Sponsored by: The FreeBSD Foundation

Now that we have mandoc, we can leave $Mdocdate$ tags as-is. Unfortunately,
there is (currently) no way to make Subversion generate correct $Mdocdate$
tags, but perhas we can teach mandoc to read Subversion's %d format.

Add a pre-merge script which reverts mechanical changes such as added
$FreeBSD$ tags and man page dates.

Add a post-merge script which reapplies these changes.

Run both scripts to normalize the existing code base. As a result, many
files which should have had $FreeBSD$ tags but didn't now have them.

Partly rewrite the upgrade instructions and remove the now outdated
list of tricks.

Upgrade to OpenSSH 6.2p1. The most important new features are support
for a key revocation list and more fine-grained authentication control.

Upgrade to OpenSSH 5.9p1.

MFC after: 3 months

More commas

Our groff doesn't understand $Mdocdate$, so replace them with bare dates.

MFC after: 3 days

Upgrade to OpenSSH 5.1p1.

I have worked hard to reduce diffs against the vendor branch. One
notable change in that respect is that we no longer prefer DSA over
RSA - the reasons for doing so went away years ago. This may cause
some surprises, as ssh will warn about unknown host keys even for
hosts whose keys haven't changed.

MFC after: 6 weeks

Now that we have mandoc, we can leave $Mdocdate$ tags as-is. Unfortunately,
there is (currently) no way to make Subversion generate correct $Mdocdate$
tags, but perhas we can teach mandoc to read Subversion's %d format.

Add a pre-merge script which reverts mechanical changes such as added
$FreeBSD$ tags and man page dates.

Add a post-merge script which reapplies these changes.

Run both scripts to normalize the existing code base. As a result, many
files which should have had $FreeBSD$ tags but didn't now have them.

Partly rewrite the upgrade instructions and remove the now outdated
list of tricks.

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

Missing commas in Dd

Approved by: re (kib@)

More commas

Create the altix project branch. The altix project will add support
for the SGI Altix 350 to FreeBSD/ia64. The hardware used for porting
is a two-module system, consisting of a base compute module and a
CPU expansion module. SGI's NUMAFlex architecture can be an excellent
platform to test CPU affinity and NUMA-aware features in FreeBSD.

- Import the HEAD csup code which is the basis for the cvsmode work.

Our groff doesn't understand $Mdocdate$, so replace them with bare dates.

MFC after: 3 days