Add Evolution Data Server (EDS) calendar integration to the MATE panel
clock applet, most of it ported from gnome-panel's clock applet. This
allows users to view calendar events and tasks directly from the clock
popup calendar.

The calendar integration is disabled by default and can be enabled
with --enable-eds during configuration. When disabled, the clock
applet functions normally without any EDS dependencies.

* Clock applet/wayland: position calendar window same as in x11

- Wayland/clock: fix calendar window rendering when moved
Ensure the calendar window cannot be "stretched" across the screen
if the panel or the applet is moved while the calendar is showing

Fix distribution of the applet service files sources when building from
an in-process-configured build.  This fixes `make distcheck` and
tarballs in builds configured with `--with-in-process-applets=all` (or
actually any in-process applet).

The issue was that the .service.in file was referenced indirectly in
EXTRA_DIST, and the variable listed there was only filled in a
conditional.  Automake is not able to resolve this and see it still
should distribute the reference of that variable, even if set
conditionally.  Fix this by always setting the variable properly, even
if it's only used for out-of-process builds.

origin commits:
https://git.gnome.org/browse/gnome-panel/commit/?h=gnome-3-4&id=aa2895d
https://git.gnome.org/browse/gnome-panel/commit/?h=gnome-3-4&id=695d30c
https://git.gnome.org/browse/gnome-panel/commit/?h=gnome-3-4&id=00f9870
https://git.gnome.org/browse/gnome-panel/commit/?h=gnome-3-4&id=9ade365

* Bump intltool required version for gsettings support
* Extract strings with intltool directly
* Let autoconf generate the xml files