Update sysdeps/unix/sysv/linux/bits/socket.h for Linux 4.6

[Christoph Hellwig]

On Tue, May 17, 2016 at 12:13:54AM +0000, Joseph Myers wrote:
> in the header, since I saw no apparent reason for the set in glibc to
> stop at SOL_IRDA.  MSG_BATCH is added; Linux also has
> MSG_SENDPAGE_NOTLAST which is not in glibc, but given the comment
> starts "sendpage() internal" I presume it's correct for it not to be
> in glibc.

But I can't see any code checking for it being passed from userspace,
which is a bit odd.

> (Note that this is a case where the Linux kernel header with userspace
> relevant values is *not* a uapi header but include/linux/socket.h - I
> don't know why, but at least this header, as well as uapi headers,
> needs reviewing for glibc-relevant changes each release.)

It would be good to just move it to a uapi header.  Can you bring this
issues up on lkml and the netdev list?