Output SPS when it changes in mp2ts-pslister

[tobbee]

mp2ts-pslister currently lists the parameter the first time any sps appears.

That is quite OK, but it would be good to have an update if new values appear.
It is therefore suggested to reset SPS (and PPS) every time a new SPS appears,
and after that report any new PPS.

For changes it would be good to get some indication on where the change happened, e.g. by outputting the PTS value of the video PES packet where the change occured