small fix for export component
As discussed with arkadini on irc, InvokeMovieExportGetPropertyUPP may return paramErr if the user wishes to use the default value for this parameter. Although poorly documented, pretty much all (Apple) export components support this. Basically, the fix is simply to return noErr instead of err at the end of configure_stream__video (in stream_video.c).
The patch also has a few added lines of code that set the values of the structures being passed to InvokeMovieExportGetPropertyUPP. This also isn't really documented, but it's done by most export components. This way, the user can change only one value of the structure (e.g. key-frame-rate) without touching the rest.
Finally, I added a InvokeMovieExportGetPropertyUPP for movieExportUseConfiguredSettings which does nothing, but reminds you that ideally, this should be checked. When set to true, you should use the preconfigured settings as a starting point for the configuration. When set to false, you should use the component's default values as a starting point.