prepare to add function to find sub-songs

for import

src/engine/fileOps/it.cpp

@@ -623,6 +623,9 @@ bool DivEngine::loadIT(unsigned char* file, size_t len) {
     }
     ds.systemLen=(maxChan+32)>>5;
 
+    // find subsongs
+    ds.findSubSongs();    
+
     if (active) quitDispatch();
     BUSY_BEGIN_SOFT;
     saveLock.lock();

src/engine/fileOps/mod.cpp

@@ -418,6 +418,9 @@ bool DivEngine::loadMod(unsigned char* file, size_t len) {
     }
     ds.insLen=ds.ins.size();
 
+    // find subsongs
+    ds.findSubSongs();
+    
     if (active) quitDispatch();
     BUSY_BEGIN_SOFT;
     saveLock.lock();

src/engine/fileOps/s3m.cpp

@@ -999,6 +999,9 @@ bool DivEngine::loadS3M(unsigned char* file, size_t len) {
       }
     }
 
+    // find subsongs
+    ds.findSubSongs();    
+
     if (active) quitDispatch();
     BUSY_BEGIN_SOFT;
     saveLock.lock();

src/engine/fileOps/xm.cpp

@@ -370,6 +370,9 @@ bool DivEngine::loadXM(unsigned char* file, size_t len) {
 
     ds.sampleLen=ds.sample.size();
 
+    // find subsongs
+    ds.findSubSongs();
+
     if (active) quitDispatch();
     BUSY_BEGIN_SOFT;
     saveLock.lock();

src/engine/song.cpp

@@ -128,6 +128,10 @@ void DivSubSong::makePatUnique() {
   }
 }
 
+void DivSong::findSubSongs() {
+
+}
+
 void DivSong::clearSongData() {
   for (DivSubSong* i: subsong) {
     i->clearData();

src/engine/song.h

@@ -353,6 +353,11 @@ struct DivSong {
   DivWavetable nullWave;
   DivSample nullSample;
 
+  /**
+   * find data past 0Bxx effects and place that into new sub-songs.
+   */
+  void findSubSongs();
+
   /**
    * clear orders and patterns.
    */