The opus audio codec from XiPH.org for arduino

This library is mainly targeted for Platform.io, because I have no idea how to specify compiler flags in Arduino library.

If someone actually DO find a way to do that, I'm open for PR.

The git checkout doesn't contain the codes from libogg, libopus, nor libopusfile, there is some more step to be done before you can compile your project with platformio. I'm doing this on a linux box, and I have no idea how to do that on windows (requires a whole bunch of gnu tools...) I accept PR if someone figure out a better way to do that, anyway.

For those people on Mac OS X or Windows, just download the release tarball FTM.

1. git submodule init
2. git submodule update
3. git submodule sync
4. run script/prepare.sh
5. done!

TBD

• this library: APACHE 2.0
• ogg: BSD-3 (link wanted!)
• opus: BSD-3
• opusfile: BSD-3