Re: minimum Meson version

I wrote:
> In the context of RHEL, it says here [1] that RHEL8 maintenance
> support runs through May 2029 while extended support runs through
> May 2031.  That would still mean we're supporting RHEL8 for another
> four years.  I'm not sure what the corresponding dates are for
> other LTS vendors.

I checked Debian and SUSE and noted that their "extended support"
windows are a lot shorter than RHEL's, just two or three years.
So maybe we shouldn't buy into RHEL's five-year window.  I do take
Jelte's point that it's unlikely somebody wants to run a bleeding-edge
PG release on a platform that's many years out from end of full
support; if they are using such a platform they probably prize
stability above all else.

Maybe we could compromise on

  If the expected PG major version release date is more than N years
  after the end of full support for an LTS distribution, that OS
  version does not need to be supported.

Defining it relative to "full support" also reduces questions about
whether extended support means the same thing to every LTS vendor.

If we set N=2 then we could drop RHEL8 support in PG 19; if we
set N=3 then it'd be PG 20 (measuring from end of full support
in May 2024).  I'd be okay with either outcome.

			regards, tom lane