Fix compilation of tst_qwidget with some compilers.
Fix compilation of tst_qwidget with some compilers.

Some compilers such as the Metroworks compiler do not like it when the
two pointers have different types so cast them to be the same.

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