Add TCP_REPAIR_WINDOW from Linux 4.8

[Florian Weimer]

* Joseph Myers:

> On Mon, 3 Oct 2016, Carlos O'Donell wrote:
>
>> And double check it doesn't need coordination if you might ever want
>> to include the UAPI header and the glibc header.
>
> Since both headers already have many of the same structures without any 
> conditionals on them, I don't think adding a new structure indicates doing 
> anything new regarding coordination.

Agreed.