Merge branch 'bc/asciidoctor-tab-width'

Asciidoctor gives a reasonable imitation for AsciiDoc, but does not
render illustration in a literal block correctly when indented with
HT by default. The problem is fixed by forcing 8-space tabs.

* bc/asciidoctor-tab-width:
Documentation: render revisions correctly under Asciidoctor
Documentation: use 8-space tabs with Asciidoctor

diff --cc Documentation/Makefile
Simple merge

diff --cc Documentation/revisions.txt
Simple merge