Please, consider changing the file name to conf.dtd. I think this better matches the internal parameter entity used in manual.xml (%configure;) and file contents (Document Type Definition, dtd).

A patch I'm working on will do the suggested rename, and also will eliminate the ⟨ entity entirely. It is the only entity reference inside a XML attribute, and a sore thumb in general.

All .ent files in doc-base, and also in the root of doc-en are in fact .dtd files, not .ent files, but these are to be slowly transformed into .ent XMl files.

I'm happy to do that change in a follow up PR. Before I make that change I will add compatibility to the docbook-cs, which should be a relative easy fix.

With .inc I was fearful it might load PHP files by accident, so I wanted to get this out of the way. Expect a follow up in the next few days.

I did not see that it was merged, so my message arrived too late. doc-base 324 already does that change, and got conflicted. I will rebase it, so a follow up PR is not necessary.