add experimental low-latency mode

do not use (yet)!

src/engine/platform/segapcm.cpp

@@ -350,6 +350,7 @@ void DivPlatformSegaPCM::reset() {
   memset(regPool,0,256);
   for (int i=0; i<16; i++) {
     chan[i]=DivPlatformSegaPCM::Channel();
+    chan[i].std.setEngine(parent);
     chan[i].vol=0x7f;
     chan[i].outVol=0x7f;
   }