Make DocBook sources namespaced again

Every DocBook source document can be namespaced (DocBook 5) or non-namespaced (DocBook 4). The set of XSL stylesheets used for producing an output document can also be namespaced or non-namespaced. Namespaced source documents should be used with namespaced stylesheets and non-namespaced source documents should be used with non-namespaced stylesheets. However, both stylesheet flavors contain processing rules which allow them to be used interchangeably for any type of source document.

Unfortunately, these processing rules became broken in version 1.79.1 of the stylesheets, which means that non-namespaced source documents can no longer be correctly transformed into man pages using namespaced stylesheets and vice versa. This problem was fixed upstream [1], but no released version of the XSL stylesheets contains that fix yet.

Back in 2016, this problem was reported as RT #43831 and allegedly fixed in commit 1b8ce3b3. However, that fix only helped for the non-namespaced version of the stylesheets - while also breaking man page generation for the namespaced flavor.

Since using namespaced DocBook sources is the current best practice (DocBook 5), make BIND DocBook sources namespaced again. When using version 1.79.1 or 1.79.2 of the XSL stylesheets, care must be taken to ensure namespaced stylesheets are used for generating BIND documentation.

[1] https://github.com/docbook/xslt10-stylesheets/issues/109

Closes #2310 (closed)