json: let read TCollection-derived classes with

TBufferJSON::ConvertFromJSONAny

In some special cases (list std::vector<> or TArrayI) class information
is not stored in JSON, therefore expected class should be provided. But
this requirement can be relaxed for TList/TObjArray/... classes.

io/io/src/TBufferJSON.cxx

@@ -1668,6 +1668,9 @@ void *TBufferJSON::JsonReadObject(void *obj, const TClass *objClass, TClass **re
       if (gDebug > 1)
          Info("JsonReadObject", "Reading object of class %s refid %u ptr %p", clname.c_str(), fJsonrCnt, obj);
 
+      if (!special_kind)
+         special_kind = JsonSpecialClass(jsonClass);
+
       // add new element to the reading map
       fReadMap[fJsonrCnt++] = ObjectEntry(obj, jsonClass);
    }