This provides a pause with a maximal latency of one call
to pf_demux from the demuxer.

This allows a more reactive pause (independant of *-caching value). It is
not yet instantaneous as vout/aout still play their buffer.

- This is needed for proper seek/pause/fast forward/...
- The decoder/packetizer do not need to scale packet length anymore as the
decoder thread do it.

No functionnal changes yet.

There is no functionnal changes + cosmetics.

It is mostly clock fields renaming.

It fixes clock prototypes.

No functionnal change yet.

The input main loop will now handles space control at the right place.

They are set to -1 if not specified.

Not sure how it's called but i guess it would have resulted in crashes or memory corruption

Seems to works but i would appreciate a review by a playlist guru