[opus] Four new releases

[Jean-Marc Valin]

Hi everyone,

I'd like to announce four new releases:
- libopus 1.3-rc2
- libopusenc 0.2
- opusfile 0.11
- opus-tools 0.2

Essentially, opus-tools now depends on both libopusenc for encoding and
on opusfile for decoding. The main difference is that opusenc is now
able to use look-ahead, which helps when encoding speech and music at
low-ish bitrates.

In terms of libopus, the main changes in this second release candidates are:
- Fixing an issue with bandwidth detection
- Enabling Ambisonics support by default
- Using mapping families 2 and 3 for Ambisonics (instead of experimental
families 253 and 254)
- Enabling hardening by default

Please give it a try as it report any problems so we can get a
high-quality 1.3 release soon.

As usual, you can get everything from the downloads page at
https://opus-codec.org/downloads/

Cheers,

	Jean-Marc