Reduce duplicates of channel struct

Add/Fix custom clock limit defines (for YMF278B)

src/engine/platform/pce.h

@@ -27,14 +27,14 @@
 #include "sound/pce_psg.h"
 
 class DivPlatformPCE: public DivDispatch {
-  struct Channel {
-    int freq, baseFreq, pitch, pitch2, note, antiClickPeriodCount, antiClickWavePos;
+  struct Channel: public SharedChannelFreq, public SharedChannelVolume<signed char> {
+    int antiClickPeriodCount, antiClickWavePos;
     int dacPeriod, dacRate, dacOut;
     unsigned int dacPos;
-    int dacSample, ins;
+    int dacSample;
     unsigned char pan;
-    bool active, insChanged, freqChanged, keyOn, keyOff, inPorta, noise, pcm, furnaceDac, deferredWaveUpdate;
-    signed char vol, outVol, wave;
+    bool noise, pcm, furnaceDac, deferredWaveUpdate;
+    signed short wave;
     int macroVolMul;
     DivMacroInt std;
     DivWaveSynth ws;
@@ -43,11 +43,8 @@ class DivPlatformPCE: public DivDispatch {
       pitch2=0;
     }
     Channel():
-      freq(0),
-      baseFreq(0),
-      pitch(0),
-      pitch2(0),
-      note(0),
+      SharedChannelFreq(),
+      SharedChannelVolume<signed char>(31),
       antiClickPeriodCount(0),
       antiClickWavePos(0),
       dacPeriod(0),
@@ -55,20 +52,11 @@ class DivPlatformPCE: public DivDispatch {
       dacOut(0),
       dacPos(0),
       dacSample(-1),
-      ins(-1),
       pan(255),
-      active(false),
-      insChanged(true),
-      freqChanged(false),
-      keyOn(false),
-      keyOff(false),
-      inPorta(false),
       noise(false),
       pcm(false),
       furnaceDac(false),
       deferredWaveUpdate(false),
-      vol(31),
-      outVol(31),
       wave(-1),
       macroVolMul(31) {}
   };