clarify encoders and muxers in sound codec short names
|Reported by:||Antoine Martin||Owned by:||alas|
When codecs were first added, there was no support for multiple muxers, but now there is...
And it makes sense to use the full specification including the muxer in the codec name, so we have to switch to the new full-name and preserve backwards compatibility.
ie: vorbis will now be called vorbis+gdp and flac will now be called flac+ogg, but older clients and servers should still be able to use the old names when connecting to newer versions of xpra.
Somewhat related to #1204.
Similar to what we did for picture encodings when we switched from the old names (x264, vpx) to the new ones (h264, vp8, vp9), translate and only use the new names internally: we must send both in hello packets in case the other end doesn't understand the new names and when parsing the data (either from the command line or from a hello packet) we convert to the new names.