If we keep them around, later passes on the same data may run into
infinite loops. We cannot fully prevent any further processing of the
data because the import can happen from deep within a hierarchy of
components and modules.
Also, separate the deprecation check from the inheritance check.
Pick-to: 6.2
Change-Id: I62ce7cd15be83f60cd72b63ab858632fbc7dea66
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Ulf Hermann