[opus] Opus 1.3-beta released

[Jean-Marc Valin]

Hi,

I just released Opus 1.3-beta. This is a beta release towards the
upcoming Opus 1.3. Changes include:
- The spec fixes in RFC 8251 are now enabled by default
- Improvements to the VAD and speech/music classification using an RNN
- Improvements to stereo speech coding at low bitrate
- Added support for ambisonics projection using mapping 3 (disabled by
default)
- Fixes to the CELT PLC

Additionally, as a way to test the upcoming update to opus-tools, we’re
providing Windows binaries built with 1.3-beta. These binaries are based
on libopusenc, which means opusenc is finally able to make use of the
Opus delayed-decision feature to make better speech/music transitions.

Source code:
https://archive.mozilla.org/pub/opus/opus-1.3-beta.tar.gz

Win32 binaries:
https://archive.mozilla.org/pub/opus/win32/opus-tools-test1.zip

Please report any issues. Have fun!

	Jean-Marc