Update Doxygen config

[joto]

Using "doxygen -u"

[kkaefer]

While looking through this, I noticed that the readme/contributing/documentation files reference a Makefile that no longer exists. Apparently, you deleted it in 2017 in 178c469 :)

[joto]

@kkaefer I can't find any mentioning of a Makefile!?

[kkaefer]

Not in the doxygen config itself, but in the rest of the readme files in our repo.

[joto]

Not in the doxygen config itself, but in the rest of the readme files in our repo.

I can't find anything there either.

[kkaefer]

I can :) See #147

[joto]

Those are not "left-overs" from before. They are just what I type in to get the job done. I don't use those cmake commands and I don't know why I should. Sure, now you can use ninja or whatever instead of make. But in the end cmake is calling the underlying tool. And I'd rather use the underlying tool directly, because cmake is hiding functionality and I know how to get the result I want with the underlying tool. Maybe I am old-fashioned.