Icecast should implement RFC 5334 / 4281 support ("codecs" Media Type parameter)

Just stumbled into this while working on Opus support in the YP server code.

Proper support for "; codecs=" as specified in RFC 5334 / 4281 in the content-type would be desireable. This could then be used to present proper information in the web interface and when submitting to YP. It would also provide hinting for listener clients.