Core: Use class, not struct

Change-Id: Ib58e10c98b2cc379f0b5559c2758aecd7daf276a
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>

src/plugins/coreplugin/iversioncontrol.h

@@ -76,8 +76,9 @@ public:
         virtual QString refreshTopic(const QString &repository) = 0;
 
     private:
-        struct TopicData
+        class TopicData
         {
+        public:
             QDateTime timeStamp;
             QString topic;
         };