QStyleSheet: use the << form of qWarning to get more info

%p just prints a pointer. The operator<<(QObject*) member will print the
class type and object name.

Change-Id: Iba4b5c183776497d8ee1fffd1564951da0c6bebc
Reviewed-by: Sérgio Martins <sergio.martins@kdab.com>

src/widgets/styles/qstylesheetstyle.cpp

@@ -1641,7 +1641,7 @@ QVector<QCss::StyleRule> QStyleSheetStyle::styleRules(const QObject *obj) const
             if (!parser.parse(&ss)) {
                 parser.init(QLatin1String("* {") + styleSheet + QLatin1Char('}'));
                 if (Q_UNLIKELY(!parser.parse(&ss)))
-                   qWarning("Could not parse stylesheet of object %p", o);
+                   qWarning() << "Could not parse stylesheet of object" << o;
             }
             ss.origin = StyleSheetOrigin_Inline;
             styleSheetCaches->styleSheetCache.insert(o, ss);