Update manual references for C17 having been published

[Jakub Jelinek]

On Wed, Oct 17, 2018 at 09:33:44PM +0000, Joseph Myers wrote:
> This patch makes references in the manual to C17 reflect it having
> been published in July 2018.  (For the reasons it took so long to get
> to ballot and publication, see the WG14 convenor's report to the last
> SC22 plenary - SC22 N5297 - where it references "A troubling new trend
> where ISO CS has begun enforcing undocumented rules that are approved
> neither by the TMB nor by the WG 14 editors, leading to a decrease in
> the usefulness of standards documents.".)
> 
> Tested with "make info html pdf".  Applied to mainline.
> 
> 2018-10-17  Joseph Myers  <joseph@codesourcery.com>
> 
> 	* doc/invoke.texi (-std=c17), doc/standards.texi (C Language):
> 	Document C17 as published in 2018.

What about c-family/c.opt ?
std=c17
C ObjC
Conform to the ISO 2017 C standard (expected to be published in 2018).

std=c18
C ObjC Alias(std=c17)
Conform to the ISO 2017 C standard (expected to be published in 2018).

std=iso9899:2017
C ObjC Alias(std=c17)
Conform to the ISO 2017 C standard (expected to be published in 2018).

std=iso9899:2018
C ObjC Alias(std=c17)
Conform to the ISO 2017 C standard (expected to be published in 2018).

Shouldn't that be adjusted too?

	Jakub