Added an optional "loaded_duration" parameter to the 'updated' message. This is the duration through which the time-based media has loaded, and should be between zero and the value of the "duration" parameter. If the parameter is not supplied, it will be implicitly set to the same value as the "duration" parameter, so the movie will appear fully loaded. This can be queried with LLPluginClassMedia::getLoadedDuration().
Made the "loaded_duration" parameter also implicitly set the progress percentage and send out MEDIA_EVENT_PROGRESS_UPDATED messages when it changes.
Made the quicktime plugin set the "loaded_duration" parameter in its update messages.