Declare the Static Const Char on the .cpp file

Since the Static const char * items are private and nothing
should access them besides the MainWindow class, declare
them inside of the .cpp file with static linkage, this way
a few good things happen: they are not exported as symbols
to any other class (not even with private linkage) and also
if we need to add a new one, on the .cpp, the only compiled
file will be the cpp, instead of the tons of files that include
mainwindow.h
Signed-off-by: Tomaz Canabrava <tomaz.canabrava@intel.com>

src/ui/MainWindow.cc

@@ -84,15 +84,16 @@ This file is part of the QGROUNDCONTROL project
 const char* MAIN_SETTINGS_GROUP = "QGC_MAINWINDOW";
 
 #ifndef __mobile__
-const char* MainWindow::_mavlinkDockWidgetName =            "MAVLink Inspector";
-const char* MainWindow::_customCommandWidgetName =          "Custom Command";
-const char* MainWindow::_filesDockWidgetName =              "Onboard Files";
-const char* MainWindow::_uasStatusDetailsDockWidgetName =   "Status Details";
-const char* MainWindow::_uasInfoViewDockWidgetName =        "Info View";
-const char* MainWindow::_hilDockWidgetName =                "HIL Config";
-const char* MainWindow::_analyzeDockWidgetName =            "Analyze";
-
-const char* MainWindow::_visibleWidgetsKey =                "VisibleWidgets";
+static const char* _mavlinkDockWidgetName = "MAVLink Inspector";
+static const char* _customCommandWidgetName = "Custom Command";
+static const char* _filesDockWidgetName = "Onboard Files";
+static const char* _uasStatusDetailsDockWidgetName = "Status Details";
+static const char* _pfdDockWidgetName = "Primary Flight Display";
+static const char* _uasInfoViewDockWidgetName = "Info View";
+static const char* _hilDockWidgetName = "HIL Config";
+static const char* _analyzeDockWidgetName = "Analyze";
+
+static const char* _visibleWidgetsKey = "VisibleWidgets";
 #endif
 
 static MainWindow* _instance = NULL;   ///< @brief MainWindow singleton

src/ui/MainWindow.h

@@ -227,15 +227,6 @@ private:
     QPointer<QWidget> _missionEditorView;
 
 #ifndef __mobile__
-    // Dock widget names
-    static const char* _mavlinkDockWidgetName;
-    static const char* _customCommandWidgetName;
-    static const char* _filesDockWidgetName;
-    static const char* _uasStatusDetailsDockWidgetName;
-    static const char* _uasInfoViewDockWidgetName;
-    static const char* _hilDockWidgetName;
-    static const char* _analyzeDockWidgetName;
-
     QMap<QString, QGCDockWidget*>   _mapName2DockWidget;
     QMap<QString, QAction*>         _mapName2Action;
 #endif
@@ -250,8 +241,6 @@ private:
     void _showDockWidget(const QString &name, bool show);
     void _loadVisibleWidgetsSettings(void);
     void _storeVisibleWidgetsSettings(void);
-
-    static const char* _visibleWidgetsKey;
 #endif
 
     bool                    _autoReconnect;