arm64 on apt.postgresql.org

# arm64 on apt.postgresql.org

The apt.postgresql.org repository has been extended to cover the arm64
architecture.

HUAWEI Cloud Services donated a arm64 build host with enough resources
to build the arm64 packages at the same speed as the existing amd64,
i386, and ppc64el architectures.

We are targeting Debian buster (stable), bullseye (testing), and sid
(unstable), and Ubuntu bionic (18.04) and focal (20.04). To use the
arm64 archive, just add the normal sources.list entry:

deb https://apt.postgresql.org/pub/repos/apt buster-pgdg main

# Ubuntu focal

At the same time, I've added the next Ubuntu LTS release to apt.postgresql.org:
focal (20.04). It ships amd64, arm64, and ppc64el binaries.

deb https://apt.postgresql.org/pub/repos/apt focal-pgdg main

# Old PostgreSQL versions

Many PostgreSQL extensions are still supporting older server versions that are
EOL. For testing these extension, server packages need to be available. I've
built packages for PostgreSQL 9.2+ on all Debian distributions, and all Ubuntu
LTS distributions. 9.1 will follow shortly.

This means people can move to newer base distributions in their .travis.yml,
.gitlab-ci.yml, and other CI files.

Christoph