Make it compile against qt6

serializers/akonadi_serializer_kcalcore.cpp

@@ -19,6 +19,7 @@
 
 #include "serializer_debug.h"
 #include <QDate>
+#include <QIODevice>
 
 using namespace KCalendarCore;
 using namespace KCalUtils;

src/blockalarmsattribute.cpp

@@ -12,6 +12,7 @@
 #include <Akonadi/AttributeFactory>
 #include <QByteArray>
 #include <QDataStream>
+#include <QIODevice>
 
 using namespace Akonadi;
 

src/kcolumnfilterproxymodel_p.h

@@ -9,8 +9,13 @@
 #pragma once
 
 #include <QSortFilterProxyModel>
-
-template<class T> class QVector;
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+template<typename T>
+class QVector;
+#else
+template<typename T>
+class QList;
+#endif
 
 namespace Akonadi
 {