Merge branch 'doc/4.3-reproducible' into docs-next

Ben Hutchings writes:

  As part of the reproducible builds project, Jérémy Bobbio identified
  several time-dependent and non-deterministic functions in the document
  build process (htmldocs, mandocs targets).  This patch series should fix
  all of those.

I ended up reverting one patch that introduced problems.

diff --cc Documentation/DocBook/Makefile
Simple merge