Problem
"Listening Side" and "Initiating Side" in the IPv6 chapter of the
Developers Handbook use level 5 headings (======). In books these
are offset and render as <h7> in single-page HTML output, failing
W3C validation and breaking the heading hierarchy.
They are not sections: they are paired remarks already introduced
by "Comments on listening side:" and "Comments on initiating side:".
Changes
- developers-handbook/ipv6/_index.adoc: replace both headings with a bold run-in lead in the following paragraph.
- FDP Primer, Asciidoctor chapter: add a WARNING that level 5 headings are unusable in books, with alternatives.
W3C validator: no more h7 errors in the Developers Handbook.
This patch will fix the last validation error in English section
of the Documentation. Other translations should sync their texts
with English documents AsciiDoc syntax.