Make QStringLiteral and QByteArrayLiteral always return the real types

Make QStringLiteral and QByteArrayLiteral always return the real types

Up until now, the macros would return an internal type that contained
the pointer to the data. This breaks code that tried to use the macros
with operators, like QStringBuilder but also when writing:

     QStringList() << QStringLiteral("a") << QStringLiteral("b");

This change seems to work fine now and I can also verify that this
works:

     const auto str = QStringLiteral("Hello");

Even though it creates a QString, which is non-POD and non-constexpr.

Change-Id: Iaf82af9bea4245513a1128ea54f9d2d3d785fb09
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@nokia.com>