Autotest: tst_QScriptEngine::newVariant()

The failure comment refers to QObject but this is testing QVariant. The QVariant prototype object should itself be a QVariant (i.e. wrapping an invalid QVariant) and have methods valueOf and toString. I don't know if anyone really relies on the QVariant prototype itself being a variant; it's just for consistency with the ECMA classes (The Number prototype is a number, the Array prototype is an array, etc).