debugger: more uiswitcher cleanup

further disentangling of debugger dockwidget updates
remove unneeded variable
make updateDockWidgetSettings private
make dockwidget eventfilter slightly less heavy

src/plugins/debugger/debuggercore.h

@@ -113,6 +113,8 @@ public:
     virtual QString gdbBinaryForToolChain(int toolChain) const = 0;
     virtual void showModuleSymbols(const QString &moduleName,
         const QVector<Symbol> &symbols) = 0;
+    virtual void openMemoryEditor() = 0;
+    virtual void languagesChanged() = 0;
 
     virtual Utils::SavedAction *action(int code) const = 0;
     virtual bool boolSetting(int code) const = 0;