QDataStream: add missing #include <iterator>

For std::distance() and std::next().

Amends 003c29511d.

Pick-to: 6.2 6.5 6.6 6.7
Task-number: QTBUG-114583
Change-Id: I6e2677aad2ab45759db2fffd17a7318d396cbc4d
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>
Reviewed-by: Marc Mutz <marc.mutz@qt.io>

src/corelib/serialization/qdatastream.h

@@ -9,6 +9,8 @@
 #include <QtCore/qcontainerfwd.h>
 #include <QtCore/qnamespace.h>
 
+#include <iterator>         // std::distance(), std::next()
+
 #ifdef Status
 #error qdatastream.h must be included before any header file that defines Status
 #endif