Minor Static Documentation Generation and Packaging Update

This is a pure bugfix release with no functional changes outside packaging and documentation.

Static Documentation Generation Updates

• Extend Makefile to also remove Cloudflare crap and generally any occurrences of unneeded <script> tags from mkdocs-generated documentation.
• Also remove generated search form, search.html and the search subdirectory.
• Remove mkdocs-generated, but completely useless sitemap.xml and sitemap.xml.gz files as they solely contain nonsense entries. Also fixes Lintian warning compressed-duplicate.

Debian Packaging Updates

• Bump debhelper compatibility level to 13.
• Drop debian/unburden-home-dir-doc.lintian-overrides, no more needed.
• Drom ancient postinst/postrm/preinst files. They were handling a configuration file name change in 2012 and nowadays even cause Lintian warnings.
• Drop adequate as-installed test as adequate is no more maintained. Also fixes Lintian warning obsolete-runtime-tests-restriction.
• Add Lintian override for uses-deprecated-adttmp. This is a false positive, it detects the code to make it backwards compatible with autopkgtest < v4.
• Declare compliance with Debian Policy 4.5.1.

Notes

This release was triggered by H01ger's request to make an upload of about 3000 arch:all Debian packages which haven't seen an upload within a specific time frame and hence lack some more recent features provided by Debian's build daemons.