ActiveAE: Add queries to determine number of channels output
[omxplayer] Make use of audio decode fast paths when downmixing

The TrueHD codec actually works in 3 stages.
It decodes the downmixed stereo.
It then decodes the differences required to produce 5.1.
It then decodes the differences required to produce 7.1.

Many users end up downmixing this 7.1 stream back to 2.0.
Much better to tell the codec we only need the 2.0 stream.

When playing a 94s duration video file on an overclocked Pi, the audio decode took:
7.1 channels: 39.6s
5.1 channels: 36.5s
2.0 channels: 23.0s

So, it's almost twice as fast to decode TrueHD when only stereo is required.
[tagloader] read popm ratings from banshee (closes #15333)
Merge pull request #4995 from mkortstiege/banshee_popm

[tagloader] read popm ratings from banshee (closes #15333)
Merge pull request #4933 from popcornmix/truhd_fast

[omxplayer] Make use of audio decode fast paths when downmixing
videoplayer: adapt lateness detection and dropping to buffering
video player: present correct pts to user for a/v sync (after buffering in renderer)
videoplayer: some rework and documentation
renderer: bump buffers to 5
videoplayer: update frametime, it might change due to fps detection
videoplayer: give streams with invalid fps a chance for fps detection
dvdplayer: allow rewinding at end of stream, do a seek after rewind
dvdplayer: observe pts counter overflow
dvdplayer: avoid short screen flicker caused by unnecessary reconfigure of renderer
vdpau: advanced settings for auto deinterlacing
player: fix rewind
OMXPlayer: some caching fixes for pvr
fix incorrect display of fps when dr kicks in
ActiveAE: slightly reduce buffer size
Revert "vdpau: comment some features that will be added later"

This reverts commit e00b4f65864d623ab4d2e9e5c06db138e661f1cf.