[opus] opus_multistream_encode_float not working in libopus 1.1

[Alpha Thinktink]

I just recently found that opus_multistream_encode_float is returning
-1 (OPUS_BAD_ARG) with the libopus 1.1 build but works just fine with
the libopus 1.0.1 and libopus 1.1-beta builds.  I tried using
opus_multistream_encoder_create and
opus_multistream_surround_encoder_create.  Tried with coupled and
uncoupled quadraphonic and uncoupled stereo encodes.  I'm dynamically
loading the libopus libraries from the pre-compiled opusfile-0.5-win32
package.

Have there been changes to the meaning or handling of the parameters
for either of the mentioned functions?