[omxplayer] Allow small audio packets to be concatenated to make better use of audio fifo

Some audio codecs produce small packets which causes a high overhead when submitting to GPU, and doesn't make full use of GPU side buffering.
TrueHD in particular can produce packets with 40 samples (so 1200 packets per second) which causes very high overhead.

What this aims to do is to concatenate audio packets until they approach the ideal audio packet size,
and then deal with the awkardness of concatenated planar formats.
[omxplayer] Use media time for determing audio delay and cache time

I've also added caching to the call to OMXMediaTime as the GPU round trip is expensive when called too frequently
Merge pull request #4777 from popcornmix/small_audio

[omxplayer] Allow small audio packets to be concatenated to make better use of audio fifo
dvdplayer: drop old remnant of masterclock
dvdplayer: let CDVDClock hold info on what is current master clock
dvdplayer: replace old frame sleep with timestamp based one

This avoid depending on frame duration in advance of next frame
dvdplayer: add support for allowing video player being master clock
dvdplayer: move selection of video reference clock to dvdplayer

CDVDPlayer is now the master of clock selection even in the
video reference clock case. This avoids the data transmission
between audio and video players for clock selection.
dvdplayer: add accessor for current clock speed adjustment to dvdclock

This avoid direct access to video reference clock in players
dvdplayer: let Discontinuity function take absolute timestamp and log

This allow caller to re-use timestamp that calculations where made on
to reduce effect from task scheduling and avoid logging corrections done.
dvdplayer: move limit check of clock discontinuity into dvd clock
dvdplayer: move sync after clock switch to UpdateClockMaster
dvdplayer: use master clock as basis for player to sync clock

TODO: move this into the players so they check on reception of packet
if they are the master of the clock.
AE: accept planar formats and timestamps at input
dvdplayer audio: simplify interface to AE, feed timestamps
paplayer: adapt to interface change of AE, feed entire frames into AE
dvdplayer: drop obsolete pcm audio codecs
AE: let player signal a discontinuity after a clock change
dvdplayer audio: remove obsolte methods and useless locks
ActiveAE: do not cut passthrough audio packets on flush