evolution-data-server D-Bus service version change in 3.29.3

[Milan Crha <mcrha redhat com>]

        Hello,
this is a little heads-up that evolution-data-server 3.29.3 release
will contain a D-Bus service version change, specifically
   org.gnome.evolution.dataserver.Sources5
changes to
   org.gnome.evolution.dataserver.Sources6

This had been done due to adding a new method to the interface for [1].
I'd not bump soname version for such API addition, but the D-Bus
service is a different thing.

I'm mentioning it here, because this influences at least Flatpak builds
of projects using evolution-data-server, like gnome-calendar,
gnome-todo and gnome-contacts, which build against the latest eds, but
run backends from the host machine (thus they do not receive all the
fixes). The Flatpak builds should be adapted accordingly.

If you think the D-Bus service version bump was unnecessary, then I
will revert it. I only thought that it was cleaner, because the C API
function will not fail due to missing D-Bus interface method (to be
honest, I do not know what the GDBusProxy will do when the running
interface doesn't contain all the methods it expects to have).

The evolution-data-server pkg-config file contains service names for
couple releases already, thus one can use:

   $ pkg-config --variable=sourcesdbusservicename evolution-data-server-1.2
   $ pkg-config --variable=addressbookdbusservicename evolution-data-server-1.2
   $ pkg-config --variable=calendardbusservicename evolution-data-server-1.2
   $ pkg-config --variable=userprompterdbusservicename evolution-data-server-1.2

to get the service names the evolution-data-server expects to have.
        Bye,
        Milan

[1] https://bugzilla.gnome.org/show_bug.cgi?id=795197