Muting track while sustained notes causes them stay for a while

[Wohlstand]

Recently I extended the functionality of the MixerX where I added the ability to mute/unmute selected tracks. I did the same ability for libADLMIDI and libOPNMIDI that using this MIDI sequencer code. However, I found here is a problem: when disabling out the track, all sustained notes launched by it, will stay active.

What we need to make:

• Force off all sustained notes launched on muting channel

Also:

• Keep all non-note events to be always sent to avoid possible glitches when the state was been missed up.

[Wohlstand]

Okay, I had to avoid the track muting, instead, I made the channel muting that works safer and more stable: additionally, it makes sure all notes on the channel were off.