Suggestion: Make it easier to use QVariant with pointers

It would be nice if using QVariant with pointers were made easier, for instance, by somehow eliminating the need to cast to and from void *.

Example usage case:

This comes up, for example, when populating a combo box and attaching an object to each item. If we want to attach a Foo* type of object to a combo box entry we do:

cb->addItem( QString(str.c_str()), QVariant::fromValue((void*)obj) );

where cb is the combo box, obj is the Foo object and str is a std::string representation of that object.

Once the user has selected an item we get the associated Foo object back
with:

int idx = cb->currentIndex();
// [...] check that idx != -1
const QVariant& data = cb->itemData( idx );
const Foo* obj = static_cast<Foo*>( data.value<void*>() );

This would be typesafe if we did not have to cast to/from void*.