docs: Remove dependency on external resources

The internals/eventloop document uses two images for
illustrative purposes, but unlike other graphics included
in the documentation these are not part of libvirt.git but
rather were added to libvirt-media.git with

  commit fae5622074cf5e18d190496f8a43260c614599b2
  Author: Michal Privoznik <mprivozn@redhat.com>
  Date:   Mon Jun 6 17:27:50 2016 +0200

    Add two event loop images

    These images are going to be used in our documentation of the
    event loop.

    Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

  fae5622074

and are requested directly from there. Specifically, the
URLs point to the libvirt.org mirror of libvirt-media.git
instead of the primary repository hosted on GitLab.

Import the images into libvirt.git so that the website
doesn't rely on external resources and can, if desired, be
browsed entirely offline from installed packages.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

docs/internals/eventloop.html.in

@@ -29,7 +29,7 @@
     not waiting for direct user input and have no graphical
     interface. Such as Libvirt.</p>
 
-    <img alt="event loop" src="https://libvirt.org/git/?p=libvirt-media.git;a=blob_plain;f=png/event_loop_simple.png;hb=HEAD"/>
+    <img alt="event loop" src="../event_loop_simple.png"/>
 
     <p>In Libvirt this approach is used in combination with
     <code>poll(2)</code> as all the communication with its
@@ -70,7 +70,7 @@
     acceptable for Libvirt. Therefore we have came up with the
     following solution.</p>
 
-    <img alt="event loop" src="https://libvirt.org/git/?p=libvirt-media.git;a=blob_plain;f=png/event_loop_worker.png;hb=HEAD"/>
+    <img alt="event loop" src="../event_loop_worker.png"/>
 
     <p>The event loop does only necessary minimum and hand over
     message processing to another thread. In fact, there can be