backporting sntrup761x25519-sha512 key exchange to OpenSSH 8.9-9.8

[Colin Watson]

On Tue, Aug 12, 2025 at 09:42:02AM +1000, Damien Miller wrote:
>If you are a maintainer for OpenSSH in a LTS operating system, please
>consider including this change, cherrypicked from the relevant branch
>for the OpenSSH release you ship (e.g. from the V_9_0 branch for
>OpenSSH 9.0). Please let me know if there is anything I can do to
>assist.

I was going to do this for Debian 12 (bookworm) which is the only 
affected Debian release, but then realized that I already did it in 
December 2024 and forgot about it. :-)

   https://bugs.debian.org/1088873

Any reason you didn't include the documentation changes from 
https://anongit.mindrot.org/openssh.git/commit/?id=aee54878255d71bf93aa6e91bbd4eb1825c0d1b9 
as well?  Encouraging distributors to keep that in sync seems like a 
good idea (and when I cherry-picked the new alias into Debian I included 
the documentation changes).

Thanks,

-- 
Colin Watson (he/him)                              [cjwatson at debian.org]