Managed TitleBar affects Control placement

[jpobst]

When using a managed TitleBar, the title bar area is considered part of the client area, and thus a Control placed at (0, 0) ends up under the title bar. When using UseSystemDecorations = true to get a system title bar, the area is not considered client area, and the control is completely visible. (The total Form size is also different.)

Controls.Add (new Panel { Left = 20, Top = 20, Width = 100, Height = 100 }).Style.BackgroundColor = SKColors.Red;