wined3d: Add surface conversion function from WINED3DFMT_YUY2 to WINED3DFMT_B8G8R8X8_UNORM (try 2)

[Stefan Dösinger]

> +            dst_line[x] = 0xff000000
> +                | cliptobyte((c2 + r2) >> 8) << 16    /* red   */
> +                | cliptobyte((c2 + g2) >> 8) << 8     /* green */
> +                | cliptobyte((c2 + b2) >> 8);         /* blue  */
I'm not sure if 0xff is the correct value for the X channel, but technically it shouldn't really matter since the X is ignored. Is there a specific reason why you set it to 0xff?

Otherwise the patch looks ok to me, but I think Henri might want to take a look at it as well before it is committed.