Fixes to allow Compilation using VC++ 12

Some minor fixes and tweaks to allow compilation under Visual C++ 12.
This doesn't include changes that I need to make to the build
generation.

src/sdr/SDRThread.cpp

@@ -262,7 +262,7 @@ void SDRThread::threadMain() {
         double time_slice = (double) n_read / (double) sampleRate;
         seconds += time_slice;
 
-        if (iqDataOutQueue != NULL) {
+        if (iqDataOutQueue.load() != NULL) {
             iqDataOutQueue.load()->push(dataOut);
         }
     }