FIX handling MIDI Conformant data in AMDTP stream

IN MMA/AMEI RP-027, MIDI streams are multiplexed into one AMDTP channel.
When de-multiplexing, the remainer of dividing Data Block Count by 8 is
a number of MIDI stream.

But Fireworks multiplexes 16 MIDI channels into one AMDTP channel.
When receiving from Fireworks, there is no problem because 16 is multiple
of 8 but when transmitting to FIreworks, one of two MIDI sequence is
dropped.

Additionally Fireworks don't allow to use multi-byte data in one MIDI
Conformant Data.

For these two exceptions, this commit add new members in amdtp_out_stream
structure and add several arguments to amdtp_out_stream_set_midi function.