PostgreSQL 17 support

[Regina Obe]

> > Or do we feel we won't be able to release 3.5.0 in time for PG17 in
> > which case we need to backport changes to 3.4 and do another 3.4
> > release.
> 
> That needs to be done anyway, I think for smoother updates.
> 
> Regards,
> 
> --
> Devrim Gündüz
> Open Source Solution Architect, PostgreSQL Major Contributor
> Twitter: @DevrimGunduz , @DevrimGunduzTR

Why does it need to be done for smoother upgrades? 
Now that we got rid of the minor, people are better off just installing one version in PG17
And the dependencies between 3.4 and 3.5 aren't that different.

In the past the issue with upgrades would have been postgis-3.4.so vs. postgis-3.5.so  prevented clean pg_upgrade
But now they are both called postgis-3.so that should no longer be an issue.

Please let me know if I am missing something here.

Thanks,
Regina