Fix space usage, useful for search/replace
Modified the way the chat window interacts with the notification core
Updated POTFILES.in
Simplified the call window code (should be better at memory management with the engine)

(only lightly tested as ekiga.net doesn't work)
Modified the way the audio event scheduler is managed (all the infrastructure was in place to properly manage it!)
Use g_usleep instead of PThread()::Current()->Sleep ()
Made sure the video preview manager thread is shut down correctly (and timely!)
Use correct unit of time in the g_usleep calls (thanks for the head-up, Eugen!)
[l10n] Updated Catalan translation
OPAL: Fixed call waiting support.
Call Window: Fixed impossibility to hangup active call after a missed call.

The call window was reset to its initial values with the hangup button
being grayed out.
Opal: Moved MessageSummary subscription to Opal::Account.

This allows subscribing/unsubscribing when enabling and disabling SIP
accounts. It should fix the bug where OPTIONS requests keep being sent
after the account has been disabled.
Shuffled the engine initialization code so plugins are initialized before the user interface
Made the base Ekiga::ConfBridge class disconnect notifiers correctly
Made the Ekiga::ConfBridge base class stop enforcing some implementation detail it doesn't need, and made all implementations cope with the change
Made the main window manage its conf notifiers more carefully
Made the assistant window manage conf notifiers more carefully
Made the preferences window manage its conf notifiers more carefully
Broke the ext window finalize into dispose&finalize

Dispose is to break reference circles and might be called several times,
while finalize is to free memory.
Made the codecsbox code manage its conf notifiers more carefully