With pre-2.0 Intel drivers in CBR mode, if an explicit SEI message with
the old (now deprecated) type is not included, the driver generates and
inserts some timing SEI which is almost certainly invlaid.  Before
7a4fac5e we always inserted our own SEI
so this would not be visible, but since then it has been possible to
disable that.  We would also like to avoid using the deprecated type,
and using the new type, while working in old drivers, does not suppress
the spurious message like the old type does.

Therefore, suppress the bad SEI insertion by providing a zero-length
buffer with the old type, which the driver can insert harmlessly.