Fix lupdate issues

- missing Q_DECLARE_TR_FUNCTIONS
- some full qualifications needed for confused lupdate
- avoid breaking some translations from former TaskListPlugin,
  VcsCommand and highlighter settings refactoring

Change-Id: Ia3b34095512a7bad6903f0aff6095313ee39e3e4
Reviewed-by: hjk <hjk@qt.io>

src/plugins/cppcheck/cppcheckplugin.cpp

@@ -39,7 +39,8 @@ public:
     CppcheckOptionsPage options;
     DiagnosticsModel manualRunModel;
     CppcheckTool manualRunTool;
-    Utils::Perspective perspective{Constants::PERSPECTIVE_ID, CppcheckPlugin::tr("Cppcheck")};
+    Utils::Perspective perspective{Constants::PERSPECTIVE_ID,
+                                   ::Cppcheck::Internal::CppcheckPlugin::tr("Cppcheck")};
     QAction *manualRunAction;
 
     void startManualRun();