MISSING HEADERS ( * = difficult, - = quick, + = placeholder, x = won't do )
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> NSATSTypesetter.h +
> NSDiffableDataSource.h *
> NSDraggingItem.h -
> NSDraggingSession.h -
> NSFilePromiseProvider.h -
> NSFilePromiseReceiver.h -
> NSItemProvider.h + 
> NSOpenGLLayer.h +
> NSTypesetter.h +
> NSUserActivity.h -
> NSWindowTab.h +
> NSWindowTabGroup.h +