Fix gcc errors

sdrgui/gui/loglabelslider.cpp

@@ -17,6 +17,8 @@
 
 #include <QDebug>
 
+#include <cmath>
+
 #include "loglabelslider.h"
 
 LogLabelSlider::LogLabelSlider(QWidget *parent) :

sdrgui/gui/logslider.cpp

@@ -19,6 +19,9 @@
 #include <QPainter>
 #include <QDebug>
 
+#include <cmath>
+
+
 #include "logslider.h"
 
 LogSlider::LogSlider(QWidget *parent) :