void return, not boolean success, from some Track virtual functions...

... The return codes were mostly ignored anyway, and exceptions will be thrown
instead.

It seems there was also confusion whether the return values of Track::Paste
and Track::SyncLockAdjust were to indicate success or indicate whether there
was any change.  No matter now.

src/AudioIO.cpp

@@ -2474,13 +2474,10 @@ void AudioIO::StopStream()
                   }
                   if( appendRecord )
                   {  // append-recording
-                     bool bResult;
                      if (recordingOffset < 0)
-                        bResult = track->Clear(mT0, mT0 - recordingOffset); // cut the latency out
+                        track->Clear(mT0, mT0 - recordingOffset); // cut the latency out
                      else
-                        bResult = track->InsertSilence(mT0, recordingOffset); // put silence in
-                     wxASSERT(bResult); // TO DO: Actually handle this.
-                     wxUnusedVar(bResult);
+                        track->InsertSilence(mT0, recordingOffset); // put silence in
                   }
                   else
                   {  // recording into a NEW track