[opus] opusfile 0.1 release

[Timothy B. Terriberry]

This is the initial release of libopusfile. Like libvorbisfile for
Vorbis files, libopusfile provides a high-level API for decoding
and seeking within .opus files. It includes:

- Support for all files with at least one Opus stream (including
   multichannel files or Ogg files where Opus is muxed with
   something else).
- Full support, including seeking, for chained files.
- A simple stereo downmixing API (allowing chained files to be
   decoded with a single output format, even if the channel count
   changes).
- Support for reading from a file, memory buffer, or over HTTP(S)
   (including seeking).
- Support for both random access and streaming data sources.
- Two simple examples demonstrating the API.

The code has undergone basic testing, but as this is the first
release, there are still likely to be issues we didn't find. Please
give feedback in #opus on irc.freenode.net or on this list.

You can download the source code here:
http://downloads.xiph.org/releases/opus/opusfile-0.1.tar.gz

Windows binaries (with HTTP support disabled) are here:
https://ftp.mozilla.org/pub/mozilla.org/opus/win32/opusfile-0.1-win32.zip