Related to https://gitlab.gnome.org/GNOME/evolution-data-server/issues/41
Closes https://gitlab.gnome.org/GNOME/evolution/issues/196
This covers bug 784208, gtk-doc generated warnings like this one: Warning: multiple "IDs" for constraint linkend: api-index-3.2.
Let's have it as it's common to be, which means top level src/ for sources, single data/ for data, and so on.