CppEditor: Do not omit the function return type

... when rewriting an argument of a refactored function.

Fixes: QTCREATORBUG-13698
Change-Id: Ifb569a290d3c46944d17a73a19400833e5ba7fe9
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/cppeditor/cppfunctiondecldeflink.cpp

@@ -639,6 +639,7 @@ ChangeSet FunctionDeclDefLink::changes(const Snapshot &snapshot, int targetOffse
         env.enter(&q);
         Control *control = sourceContext.bindings()->control().data();
         Overview overview = overviewFromCurrentProjectStyle;
+        overview.showReturnTypes = true;
 
         // make a easy to access list of the target parameter declarations
         QVarLengthArray<ParameterDeclarationAST *, 10> targetParameterDecls;