It is tedious to test all the overloads of QString::prepend,
so get the help of the compiler to do it. The framework
was originally developed for testing append.
This change showed that prepend(QStringRef) and
prepend(const QChar*, int) overloads were missing. They will
be added in a separate commit.
Change-Id: Ic3d6ad011bedc6ee7d5024094d7c3529b1b9d669
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>