yamaha: new GEW7 and GEW12 machines, various GEW8/MultiPCM improvements (#11105)
* yamaha: implement GEW7, partially implement GEW12, some GEW8/MultiPCM fixes (envelope behavior, sample lengths, stream updates, save state members)
New working machines
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Yamaha PSR-150 [Edward d-tech, Devin Acker]
Yamaha PSR-180 [Edward d-tech, Devin Acker]
Yamaha PSR-78 [Edward d-tech, Devin Acker]
New working clones
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Yamaha PSR-110 [Edward d-tech, Devin Acker]
Yamaha PSR-75 [Edward d-tech, Devin Acker]
Yamaha PSR-76 [Edward d-tech, Devin Acker]
Yamaha PSS-11 [Edward d-tech, Devin Acker]
Yamaha PSS-21 [Edward d-tech, Devin Acker]
Yamaha PSS-31 [Edward d-tech, Devin Acker]
Yamaha PSS-6 [Devin Acker]
Machines promoted to working
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Yamaha PSS-12 [Devin Acker]
New NOT_WORKING machines
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Yamaha PSR-260 [Edward d-tech, Devin Acker]
Yamaha PSR-79 [Edward d-tech, Devin Acker]
New NOT_WORKING clones
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Yamaha PSR-160 [Edward d-tech, Devin Acker]