[opus] Opus for ASR

[Young, Milan]

> From: Jean-Marc Valin [mailto:jmvalin at jmvalin.ca]
> To be honest, I don't think any "ASR mode" would make enough difference
> that it would be worth signalling that over the wire. As long as APIs turn it on
> for the encoder, it should be enough. In any case, let's not worry about that
> until there's actually something worth showing.

[Milan] Sorry, my intentions were not properly communicated.  I agree that we should prefer to avoid ASR optimizations that affect decoding.  As such it's likely that no additional wire signaling will be necessary.