Don't use QStringLiteral in comparisons

For QLatin1String, operator== is overloaded, so comparing to a latin-1
(C) string literal is efficient, since strlen() is comparatively fast.

OTOH, QStringLiteral, when not using RVO, litters the code with
QString dtor calls, which are not inline. Worse, absent lambdas,
it even allocates memory.

So, just compare using QLatin1String instead.

Change-Id: I761b2b26ab5b416bc695f524a9ee607dacf0a7b2
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>