So
#include <QtCore/qdatetime.h>
#include <QtCore/qcryptographichash.h>
needs to become:
#include <QtCore/qdatetime.h>
#include <QtCore/qcryptographichash.h>
#include <QtCore/qdatastream.h>
Otherwise I did not manage to get the library compiled on Qt 5.5 with MS Visual Studio 2013.