docbook reader: fix nesting of chapters and sections (#5864)

2019-10-30T15:51:33Z

* Set dbBook to true when traversing a chapter too. Currently, a `` in a chapter and in a `<section/>` below that chapter have the same level if they're not inside a `<book/>`. This can happen in a multi-file book project. Also see the example at https://tdg.docbook.org/tdg/4.5/chapter.html Co-authored-by: Félix Baylac-Jacqué <felix@alternativebit.fr> * Add docbook-chapter test This tests nested `<section/>` and makes sure `<title/>` in the first `<section/>` below `<chapter/>` is one level deeper than the `<chapter/>`'s `<title/>`, also when not inside a `<book/>`. Co-authored-by: Félix Baylac-Jacqué <felix@alternativebit.fr> </article> </main></body></html>

pandoc/test/docbook-chapter.docbook, branch master

docbook reader: fix nesting of chapters and sections (#5864)