RigCtrl plugin: removed QtWidgets dependencies from where they should not be

plugins/misc/rigctrl/readme.md

@@ -2,7 +2,7 @@
 
 <h2>Introduction</h2>
 
-The rigctrl plugin allows SDRangel to be controlled via ![Hamlib](http://hamlib.sourceforge.net/manuals/hamlib.html)'s rigctrld protocol. This allows other software that implements the rigctrld protocol, such at the satelite tracking software GPredict, to control SDRangel, to adjust for doppler or to automatically switch between different satellite frequencies and modes.
+The rigctrl plugin allows SDRangel to be controlled via [Hamlib](http://hamlib.sourceforge.net/manuals/hamlib.html)'s rigctrld protocol. This allows other software that implements the rigctrld protocol, such at the satelite tracking software GPredict, to control SDRangel, to adjust for doppler or to automatically switch between different satellite frequencies and modes.
 
 <h2>Interface</h2>
 

plugins/misc/rigctrl/rigctrlplugin.cpp

@@ -17,10 +17,6 @@
 
 #include <QtPlugin>
 #include <QtDebug>
-#include <QtWidgets/QAction>
-#include <QtWidgets/QMainWindow>
-#include <QtWidgets/QMenu>
-#include <QtWidgets/QMenuBar>
 
 #include "plugin/pluginapi.h"
 #include "util/simpleserializer.h"
@@ -28,6 +24,10 @@
 #include "rigctrl.h"
 #ifdef SERVER_MODE
 #else
+#include <QtWidgets/QAction>
+#include <QtWidgets/QMainWindow>
+#include <QtWidgets/QMenu>
+#include <QtWidgets/QMenuBar>
 #include "rigctrlgui.h"
 #endif
 #include "rigctrlplugin.h"
@@ -65,6 +65,7 @@ bool RigCtrlPlugin::createTopLevelGUI(
         QMainWindow* mainWindow
         )
 {
+    (void) mainWindow;
     return true;
 }
 

plugins/misc/rigctrl/rigctrlplugin.h

@@ -23,6 +23,7 @@
 #include "rigctrl.h"
 
 class PluginAPI;
+class QMainWindow;
 
 #define RIGCTRL_DEVICE_TYPE_ID "sdrangel.misc.rigctrl"
 

sdrbase/plugin/plugininterface.h

@@ -3,10 +3,11 @@
 
 #include <QtPlugin>
 #include <QString>
-#include <QtWidgets/QMainWindow>
 
 #include "export.h"
 
+class QMainWindow;
+
 struct SDRBASE_API PluginDescriptor {
     const QString hardwareId;
 	// general plugin description