Even better thread and application termination:

- Now that timed-pop()/try_pop() prevent indefinite blocking it is best to flush() on thread stopping to unblock push()
- Reworked a bit the CubicSDR::OnExit() sequence, see comments.

src/sdr/SDRPostThread.cpp

@@ -225,8 +225,9 @@ void SDRPostThread::run() {
         iqVisualQueue->flush();   
     }
 
-    //    buffers.purge();
-    //    visualDataBuffers.purge();
+    iqDataInQueue->flush();
+    iqDataOutQueue->flush();
+    iqActiveDemodVisualQueue->flush();
 
 //    std::cout << "SDR post-processing thread done." << std::endl;
 }

src/sdr/SoapySDRThread.cpp

@@ -377,8 +377,7 @@ void SDRThread::readLoop() {
         updateSettings();
         readStream(iqDataOutQueue);
     }
-
-    buffers.purge();
+    iqDataOutQueue->flush();
 }
 
 void SDRThread::updateGains() {