opus_multistream_encoder_ctl(st, OPUS_RESET_STATE) unimplemented

Under opus_multistream_encoder_init(), the Opus Multistream API documentation states:

To reset a previously initialized state, use the OPUS_RESET_STATE CTL.

However, opus_multistream_encoder_ctl(st, OPUS_RESET_STATE) returns OPUS_UNIMPLEMENTED.

Workaround: Destroy encoder and create a new one.