BT:Fix a clipping issue in tabbar tabs
BT:Fix a clipping issue in tabbar tabs

On XP and Vista where tabs use taboverlap, the currently
dragged would loose the outline. We need to compensate for the
taboverlap when creating the draggable widget, otherwise the
outline will be clipped.

Task-number: 254453
Reviewed-by: nrc

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