Painting fix when devicePixelRatio > 1

Qt draws lines on half-pixel boundaries. Because of
rounding, this is not visible with non-scaled aliased
painting. However, on a high-DPI screen with scaling
enabled, the line under the menu bar is drawn at a one
pixel offset, which causes it to overlap the menubar items.

This change draws the line at the mathematically correct position.

Task-number: QTBUG-38858
Change-Id: I0a2260507d346b52a36258d479cde87064d991ef
Reviewed-by: Alessandro Portale <alessandro.portale@digia.com>

src/plugins/coreplugin/manhattanstyle.cpp

@@ -778,7 +778,8 @@ void ManhattanStyle::drawControl(ControlElement element, const QStyleOption *opt
             Utils::StyleHelper::menuGradient(painter, option->rect, option->rect);
             painter->save();
             painter->setPen(Utils::StyleHelper::borderColor());
-            painter->drawLine(option->rect.bottomLeft(), option->rect.bottomRight());
+            painter->drawLine(option->rect.bottomLeft() + QPointF(0.5, 0.5),
+                              option->rect.bottomRight() + QPointF(0.5, 0.5));
             painter->restore();
         }
         break;