Add MADV_WIPEONFORK, MADV_KEEPONFORK from Linux 4.14

[Florian Weimer]

On 11/15/2017 07:31 PM, Joseph Myers wrote:
> 2017-11-15  Joseph Myers<joseph@codesourcery.com>
> 
> 	* sysdeps/unix/sysv/linux/bits/mman-linux.h
> 	[__USE_MISC] (MADV_WIPEONFORK): New macro.
> 	[__USE_MISC] (MADV_KEEPONFORK): Likewise.
> 	* sysdeps/unix/sysv/linux/hppa/bits/mman.h
> 	[__USE_MISC] (MADV_WIPEONFORK): Likewise.
> 	[__USE_MISC] (MADV_KEEPONFORK): Likewise.

I double-checked the constants against the kernel sources. Looks good.

Thanks,
Florian