[opus] Documentation inconsistencies

[Bruno Randolf]

Hello!

First of all Thanks for such a great codec!

I have noticed a few smaller inconsistencies in the documentation, which
may be confusing:

* Encoder related CTLs

OPUS_GET_SAMPLE_RATE(x)
"Gets the sampling rate the encoder or decoder was initialized with.
This simply returns the Fs value passed to opus_encoder_init() or
opus_decoder_init()."

---> Is it a generic CTL?

OPUS_GET_LAST_PACKET_DURATION(x)
"Gets the duration (in samples) of the last packet successfully decoded
or concealed."

---> Is it a decoder CTL?

* Generic CTLs

OPUS_GET_PITCH(x)	
"Gets the pitch of the last decoded frame, if available.

This can be used for any post-processing algorithm requiring the use of
pitch, e.g. time stretching/shortening. If the last frame was not
voiced, or if the pitch was not coded in the frame, then zero is returned.

This CTL is only implemented for decoder instances."

--> So it's a decoder CTL?

Please CC: me if you want me to read it, as I am not subscribed to your
mailing list.

Thanks,
Bruno