QmlDebug: Enable 'What are the prerequisites?' link in run configuration

DebuggerLanguageChooser is in utils, which is why we cannot directly open
the URL in the help plugin.

src/plugins/coreplugin/helpmanager.h

@@ -71,7 +71,6 @@ public:
 
     QUrl findFile(const QUrl &url) const;
     QByteArray fileData(const QUrl &url) const;
-    void handleHelpRequest(const QString &url);
 
     QStringList registeredNamespaces() const;
     QString namespaceFromFile(const QString &file) const;
@@ -87,6 +86,9 @@ public:
     void removeUserDefinedFilter(const QString &filter);
     void addUserDefinedFilter(const QString &filter, const QStringList &attr);
 
+public slots:
+    void handleHelpRequest(const QString &url);
+
 signals:
     void setupFinished();
     void documentationChanged();