dev98 - YM2612: add Fractal system

partially done

src/engine/song.h

@@ -111,6 +111,8 @@ enum DivSystem {
   DIV_SYSTEM_NAMCO,
   DIV_SYSTEM_NAMCO_15XX,
   DIV_SYSTEM_NAMCO_CUS30,
+  DIV_SYSTEM_YM2612_FRAC,
+  DIV_SYSTEM_YM2612_FRAC_EXT,
   DIV_SYSTEM_DUMMY
 };
 
@@ -394,6 +396,7 @@ struct DivSong {
   bool snDutyReset;
   bool pitchMacroIsLinear;
   bool oldOctaveBoundary;
+  bool noOPN2Vol;
 
   std::vector<DivInstrument*> ins;
   std::vector<DivWavetable*> wave;
@@ -487,7 +490,8 @@ struct DivSong {
     fbPortaPause(false),
     snDutyReset(false),
     pitchMacroIsLinear(true),
-    oldOctaveBoundary(false) {
+    oldOctaveBoundary(false),
+    noOPN2Vol(false) {
     for (int i=0; i<32; i++) {
       system[i]=DIV_SYSTEM_NULL;
       systemVol[i]=64;