prepare for adding wavetable from file

src/engine/engine.cpp

@@ -2535,6 +2535,13 @@ int DivEngine::addWave() {
   return waveCount;
 }
 
+bool DivEngine::addWaveFromFile(const char* path) {
+  isBusy.lock();
+  // TODO
+  isBusy.unlock();
+  return true;
+}
+
 void DivEngine::delWave(int index) {
   isBusy.lock();
   if (index>=0 && index<(int)song.wave.size()) {

src/engine/engine.h

@@ -325,6 +325,9 @@ class DivEngine {
     // add wavetable
     int addWave();
 
+    // add wavetable from file
+    bool addWaveFromFile(const char* path);
+
     // delete wavetable
     void delWave(int index);