QDateTime::fromSecsSinceEpoch() multiplies by 1000 but does not check
for overflow. That means we must do so in QCborValue validation. We
can't use mul_overflow<qint64> on 32-bit platforms, so we do a compare-
and-branch there. For 64-bit platforms, we prefer to do the
multiplication with checked overflow, as the common case is that it will
not overflow and we'll need the multiplication anyway.
Change-Id: Ibdc95e9af7bd456a94ecfffd16060cba6f1c86b8
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
52a2505672