reference player work

memory usage cap, garbage collection and sinc interpolation
also ability to set playback position to a negative value

src/engine/playback.cpp

@@ -3248,6 +3248,10 @@ void DivEngine::nextBuf(float** in, float** out, int inChans, int outChans, unsi
   }
   if (curFilePlayer!=NULL) {
     curFilePlayer->mix(filePlayerBuf,outChans,size);
+  } else {
+    for (int i=0; i<DIV_MAX_OUTPUTS; i++) {
+      memset(filePlayerBuf[i],0,size*sizeof(float));
+    }
   }
 
   // process metronome