Application object must be constructed before QScriptEngine
Application object must be constructed before QScriptEngine

This is required due to the switch to the JavaScriptCore-based
back-end.
Instead of segfaulting somewhere inside JSC::initializeThreading(),
call qFatal() when this constraint has been violated.

Reviewed-by: Simon Hausmann
(cherry picked from commit fb4e81bdc692efe0db9aa38dd2b941578c0f0370)

pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,igor-sfdc/qt-wk,igor-sfdc/qt-wk,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk