[Mono-winforms-list] Managed window patch

[George Giolfan]

At least on Windows, when you click on the left-most part of a title bar button it does not respond. The title buttons work as if the x coordinate of the mouse click is translated to the left by an ammount equal to the border width.
I tried adding
			x += BorderWidth;
to InternalWindowsManager.NCClientToNC and it seems to fix it, but I don't know how it affects other parts of the code.