[release] version bump to 13.0 alpha6 as we start new merge window.
Merge pull request #2915 from MartijnKaijser/bump

[release] version bump to 13.0 alpha6 as we start new merge window.
[rbp/omxplayer] Avoid resampling in audio_mixer

audio_mixer output defaults to 44.1kHz. Set it to output of audio_decode to avoid a resampling step
This restores the behaviour prior to #2801
Replace deprecated CodedID and CODEC_ID by their av prefixed counterparts.
Merge pull request #2878 from aballier/codecid

Replace deprecated CodecID and CODEC_ID_* by AVCodecID and AV_CODEC_ID_* everywhere in xbmc code.
[rbp/omxplayer] Make audio_render configurable as the clock master

By default audio_render is the clock master, and if output samples don't fit the timestamps, it will speed up/slow down the clock.
This tends to be better for maintaining audio sync and avoiding audio glitches, but can affect video/display sync.
The other option makes audio_render the clock slave, and it has to drop packet or output silence to maintain sync.

As both settings have some advantages, and as this mode more accurately defines whether playback is synced to display or audio, I've used the GUI setting "sync playback to display" to control this.

The previous use of "sync playback to display" didn't have any benefits, and was never recommended.
[rbp/omxplayer] It never makes sense to delay in audio/video players

We are not synchonous with frames submitted so sleeping won't help anything
[rbp/omxplayer] Remove fixPreroll parameter

The preroll only affects when the clock component starts. It doesn't affect the reported timestamps,
so adjusting timestamp by the preroll is incorrect
Merge pull request #2917 from popcornmix/avoid_resampling_mixer

[rbp/omxplayer] Avoid resampling in audio_mixer
Merge pull request #2922 from popcornmix/audio_clock_master

[rbp/omxplayer] Make audio_render configurable as the clock master
Merge pull request #2924 from popcornmix/remove_fixpreroll

[rbp/omxplayer] Remove fixPreroll parameter
Merge pull request #2923 from popcornmix/remove_delay

[rbp/omxplayer] It never makes sense to delay in audio/video players