[opus] Opus 1.3-rc released

[Jean-Marc Valin]

Hi,

I just released Opus 1.3-rc. This is a release candidate for the
upcoming Opus 1.3. Changes include:
- Making it possible to use SILK down to bitrates around 5 kb/s
- Using wideband encoding down to 9 kb/s
- Improving security (including a new --enable-hardening option)
- Minor quality improvement on tones
- Improving Ambisonics support (still experimental)
- Minor bug fixes

It's likely that both hardening (--enable-hardening) and ambisonics
(--enable-ambisonics) will be enabled by default in 1.3-final, so please
give those a try.

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

Win32 binaries (experimental):
https://archive.mozilla.org/pub/opus/win32/opus-tools-test-1.3-rc.zip

Cheers,

	Jean-Marc