OS X: Retina displays and blurry QToolButton

Checkable QToolButton has a special pixmap in the background,
painted with a 'smooth pixmaps' hint. This hint also affects
how an icon on a toolbutton itself is painted later. The difference
can be quite visible on a Retina display, so this patch makes the toolbutton's
image always look the same in checked/unchecked state.

Task-number: QTBUG-35162
Change-Id: I2adc8006371fa10d89d4b77da6b3aa168aa5abc8
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>

src/widgets/styles/qmacstyle_mac.mm

@@ -6005,8 +6005,10 @@ void QMacStyle::drawComplexControl(ComplexControl cc, const QStyleOptionComplex
                         p->fillPath(path, brush);
                     } else if (QSysInfo::MacintoshVersion >= QSysInfo::MV_10_5) {
                         static QPixmap pm(QLatin1String(":/qt-project.org/mac/style/images/leopard-unified-toolbar-on.png"));
+                        p->save();
                         p->setRenderHint(QPainter::SmoothPixmapTransform);
                         QStyleHelper::drawBorderPixmap(pm, p, tb->rect, 2, 2, 2, 2);
+                        p->restore();
                     } else {
                         QPen oldPen = p->pen();
                         p->setPen(QColor(0, 0, 0, 0x3a));