QSignalMapper, Feature Request for additional types

The QSignalMapper currently only supports a few basic data types (int,
QString, QWidget & QObject). To ease a more general usage of the
SignalMapper it would be nice if more datatypes could be sent with the
mapped signal, i.e. double, QList, etc. A very general usage should be
possible if QVariant would be supported as mapping argument or if there
were a template version so one could instantiate an appropriate version
of QSignalMapper.