Log Message:
Update libcanberra to 0.30

Motivation: Version 0.30 released; Port to GStreamer 1.0.

I believe the warning in doc/TODO:

   o libcanberra-0.28 [drops support for GNOME2; don't update for now -- wiz]

comes from:

Version 0.28 released; Hook properly into GNOME 3.0 sessions; this
drops support for GNOME 2.0 sessions, but not applications.

which essentially comes from:

index aa0a3a3..210d2c1 100644
--- a/src/libcanberra-login-sound.desktop.in
+++ b/src/libcanberra-login-sound.desktop.in
@@ -4,6 +4,6 @@ Name=GNOME Login Sound
 Comment=Plays a sound whenever you log in
 Exec=@bindir@/canberra-gtk-play --id="desktop-login" \ 
--description="GNOME Login"
 OnlyShowIn=GNOME;
-AutostartCondition=GNOME /desktop/gnome/sound/event_sounds
+AutostartCondition=GSettings org.gnome.desktop.sound event-sounds
 X-GNOME-Autostart-Phase=Application
 X-GNOME-Provides=login-sound

AFAICT, given that I have not found a desktop-login audio file anywhere
in pkgsrc (there is a login file), --id="desktop-login" will never match,
so we can't break something which doesn't work. If this analysis is wrong,
changing one line in 2 .desktop files is trivial. Relying on
gstreamer 0.10 working is worse.