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/mesonprojectmanager/mesonactionsmanager.h

@@ -14,7 +14,8 @@ class MesonActionsManager : public QObject
 {
     Q_OBJECT
     Utils::ParameterAction buildTargetContextAction{
-        Tr::tr("Build"), Tr::tr("Build \"%1\""),
+        ::MesonProjectManager::Tr::tr("Build"),
+        ::MesonProjectManager::Tr::tr("Build \"%1\""),
         Utils::ParameterAction::AlwaysEnabled /*handled manually*/
     };
     QAction configureActionMenu;