Currently, we stick to legacy application/ogg for legacy extensions.

but take only the first one.

Initial patch by Hannes Domani with the comments:
"Hello

 this fixes the problem when font is not attached in mkv.

 was mentioned in:
 http://forum.videolan.org/viewtopic.php?f=14&t=51096&p=166340
 http://forum.videolan.org/viewtopic.php?f=7&t=50534&p=163900
"

I used customEvent to implement it.
(It renders the dedicated message thread per subscriber useless with qt4).

Otherwise, we would have to either ignore errors, or fail to load some
plugins just because earlier ones failed

...rather than when disabling it. Otherwise service discovery plugins
cannot possibly cleanup after themselves (and CABOOM).

Whatever would need this would be a buggy SD plugin.

A destructor would never have to release its own object, since the
destructor is only called when the object is not referenced anymore.
On the other hand, it is not clear to me whether SD objects still need
a destructor.

Otherwise, if the interface is hidden behind another window, clicking
the tray icon however many times will request user attention in the task
bar and never actually show the interface. This was confusing and
inconvenient (fixes #2396). This new behavior is consistent with KMail.

It would probably be even better to show the interface on top (instead
of hiding it, then show it on the second click). Unfortunately, while it
does seem possible, I do not know how. For sure, the previous scheme did
not work anyway.