Fix non-needed usage of QString's fromLocal8Bit() and fromUtf8()

QString::fromLocal8Bit() and QString::fromUtf8() are much more slower
than an obvious QString::fromLatin1() and QLatin1String(), so this
commit changes some places where these functions are really not
needed.

QString::fromLatin1() is used in case if QString object is used
immediately (something like QString::fromLatin1().arg()),
QLatin1String is used otherwise like in other places (for example,
QPixmap(QLatin1String("..."))) - to allow to use default QString
constructor and work with QT_NO_CAST_FROM_ASCII.

Change-Id: Ib6eb1c61e9cb35c7c5b7569fea77c5e41d32621a
Reviewed-by: hjk <qthjk@ovi.com>