libsflphone_client_gnome.la must depend on the various
libtool libs (libconfig.la etc.) through the libsflphone_client_LIBADD variable

Part of gtk2->gtk3 migration

This was breaking clutter embed behaviour.

We need GTK3 to use the recent, non-broken clutter-gtk-1.0
Completely drop GTK2 compatibility

TODO: - help dialog
      - migrate to GSettings instead of gconf (not mandatory)
      - fix runtime warnings about the dynamic toolbar (hangup buttons etc)

Fallback on cairo for video display if clutter doesn't work
Use the same rgb format for clutter and cairo renderers (BGRA)
Fix a flaw in design (client needed to tell the daemon which format it needed)

gnome: rename video_preview.{c,h} into video_renderer.{c,h} and move dbus_stop_video_preview() call into videoconf.c

We want to hangup if the user closed the window, not if the window went
away due to being put on hold.