LanguageClient: add action to open call hierarchy

Fixes: QTCREATORBUG-28839
Fixes: QTCREATORBUG-28842
Change-Id: Icb70412282c0c2c36241559d942a58ffddab5664
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/languageclient/languageclientmanager.h

@@ -83,6 +83,7 @@ signals:
     void clientInitialized(Client *client);
     void clientRemoved(Client *client);
     void shutdownFinished();
+    void openCallHierarchy();
 
 private:
     LanguageClientManager(QObject *parent);