Qt5: Compile fix for generate-ast.

1. Earlier refactoring did not adapt usages here.
2. Compile with Qt5.

Change-Id: Ic461f2acb03d51e9ad903c4aa65b7d9e6d80fe86
Reviewed-by: hjk <qthjk@ovi.com>

src/libs/cplusplus/OverviewModel.cpp

@@ -238,6 +238,7 @@ Symbol *OverviewModel::symbolFromIndex(const QModelIndex &index) const
 
 void OverviewModel::rebuild(Document::Ptr doc)
 {
+    beginResetModel();
     _cppDocument = doc;
-    reset();
+    endResetModel();
 }