QThread::start(): priority has no effect on Linux systems
QThread::start(): priority has no effect on Linux systems

The default scheduling policy on Linux doesn't allow specifying thread
priorities, so the priority passed to start() and setPriority() has no
effect. Document this.

Task number: 249997
Reviewed-by: Kavindra Devi Palaraja <3f1152e99c3853ab604db3396c7031d9e0391f6e@nokia.com>
(cherry picked from commit 638b61dec0d335b12d48fe561b19a0f0f6ef83a3)

RLovelett/qt,radekp/qt,igor-sfdc/qt-wk,radekp/qt,radekp/qt,pruiz/wkhtmltopdf-qt,KDE/qt,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,radekp/qt,KDE/qt,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,RLovelett/qt,KDE/qt,KDE/qt,radekp/qt,KDE/qt,radekp/qt,RLovelett/qt,pruiz/wkhtmltopdf-qt,RLovelett/qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,KDE/qt,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,KDE/qt,igor-sfdc/qt-wk,RLovelett/qt,RLovelett/qt,radekp/qt,radekp/qt,KDE/qt,igor-sfdc/qt-wk,RLovelett/qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,RLovelett/qt,pruiz/wkhtmltopdf-qt,RLovelett/qt,RLovelett/qt,igor-sfdc/qt-wk,radekp/qt,radekp/qt,RLovelett/qt,pruiz/wkhtmltopdf-qt