pkg-config now transitional.

Given the binary package name, manpage etc. were all renamed, there are
no file conflicts and thus there is no reason to have these
break/replaces.

The override added for #787844 is unfortunately incomplete, rendering
the clean target ineffective, and resulting into a dirty source tree.

Properly override dh_auto_clean to always return the source tree to the
pristine condition.

Remove the dh_auto_build override as well, as debhelper will
automatically run dh_auto_clean first anyway.

Closes: #1047095

Avro support requires libserdes, which is not in Debian. We are passing
--enable-avro, but that does not actually take any effect, and thus both
the flag and the associated build-dependency on libavro-dev is
superfluous.

Changes-By: lintian-brush
Fixes: lintian: out-of-date-standards-version
See-also: https://lintian.debian.org/tags/out-of-date-standards-version.html

Changes-By: lintian-brush
Fixes: lintian: upstream-metadata-file-is-missing
See-also: https://lintian.debian.org/tags/upstream-metadata-file-is-missing.html
Fixes: lintian: upstream-metadata-missing-bug-tracking
See-also: https://lintian.debian.org/tags/upstream-metadata-missing-bug-tracking.html

Changes-By: lintian-brush
Fixes: lintian: trailing-whitespace
See-also: https://lintian.debian.org/tags/trailing-whitespace.html

They require a running broker.

* Build-Depends: Drop versioned constraint on librdkafka-dev and libyajl-dev.

Changes-By: deb-scrub-obsolete

Collapse debian branch onto master

The big rename from kafkacat to kcat

.. to keep credits use down.

Apache Software Foundation (ASF) trademark policies prohibits the use
of an Apache project name as part of a non-Apache project name.
In this case it was the use of `kafka` in `kafkacat` that had to be changed.

Apart from the name change there are no functional differences.
The now deprecated kafkacat.conf and KAFKACAT_CONF file and env vars
will continue to work for some time, but users should change to
kcat.conf and KCAT_CONF.