more changes to autoNoteOn

now that there's a second prefer ins type, we get rid of DIV_INS_AMIGA check

src/engine/engine.h

@@ -523,6 +523,9 @@ class DivEngine {
     // get preferred instrument type
     DivInstrumentType getPreferInsType(int ch);
 
+    // get alternate instrument type
+    DivInstrumentType getPreferInsSecondType(int ch);
+
     // get song system name
     const char* getSongSystemName();