Fix rotation of text in vertical QDockWidget titlebars in QFusionStyle.

Presumably this was just an omission when QFusionStyle was first
written. These three lines were taken directly from the equivalent
portion of QWindowsStyle and seem to work as expected.

Task-number: QTBUG-31904
Change-Id: I2f288d3cf2bfa3fe4f7f4a71e2726a172ec8e1b3
Reviewed-by: Jens Bache-Wiig <jens.bache-wiig@digia.com>

src/widgets/styles/qfusionstyle.cpp

@@ -1219,6 +1219,10 @@ void QFusionStyle::drawControl(ControlElement element, const QStyleOption *optio
                                   - titleRect.bottom(),
                                   r.top() + titleRect.left() - rect.left(),
                                   titleRect.height(), titleRect.width());
+
+                painter->translate(r.left(), r.top() + r.width());
+                painter->rotate(-90);
+                painter->translate(-r.left(), -r.top());
             }
 
             if (!dwOpt->title.isEmpty()) {