ScrollWindow fix for windows with WS_CLIPCHILDREN style, with tests

[Dmitry Timoshkov]

"Rein Klazes" <wijn at wanadoo.nl> wrote:

> -        hDC = GetDCEx( hwnd, 0, DCX_CACHE | DCX_USESTYLE );
> +        if( !(flags & SW_SCROLLCHILDREN &&
> +                GetWindowLongPtrW( hwnd, GWL_STYLE) & WS_CLIPCHILDREN))

Window style is a 32-bit entity in both Win32 and Win64, there is no need
to use GetWindowLongPtr to retrieve it, GetWindowLong should work just fine.

-- 
Dmitry.