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.

Documentation/DocBook/Makefile

@@ -56,7 +56,7 @@ htmldocs: $(HTML)
 
 MAN := $(patsubst %.xml, %.9, $(BOOKS))
 mandocs: $(MAN)
-	find $(obj)/man -name '*.9' | xargs gzip -f
+	find $(obj)/man -name '*.9' | xargs gzip -nf
 
 installmandocs: mandocs
 	mkdir -p /usr/local/man/man9/

Documentation/DocBook/stylesheet.xsl

@@ -5,6 +5,7 @@
 <param name="funcsynopsis.tabular.threshold">80</param>
 <param name="callout.graphics">0</param>
 <!-- <param name="paper.type">A4</param> -->
+<param name="generate.consistent.ids">1</param>
 <param name="generate.section.toc.level">2</param>
 <param name="use.id.as.filename">1</param>
 </stylesheet>