Handle unused variable warnings

src/GAudioOutput.cc

@@ -84,6 +84,7 @@ GAudioOutput::~GAudioOutput()
 void GAudioOutput::mute(bool mute)
 {
     // XXX handle muting
+    Q_UNUSED(mute);
 }
 
 bool GAudioOutput::isMuted()

src/audio/QGCAudioWorker.cpp

@@ -89,7 +89,6 @@ void QGCAudioWorker::say(QString text, int severity)
     {
         // TODO Add severity filter
         Q_UNUSED(severity);
-        bool res = false;
 
         if (!emergency)
         {