[Patch] Inline Variables for the Standard Library (p0607r0)

[Tim Song]

On Sat, Mar 11, 2017 at 1:32 PM, Daniel Krügler
<daniel.kruegler@gmail.com> wrote:
> This patch applies inline to all namespace scope const variables
> according to options A and B2 voted in during the Kona meeting, see:
>
> http://wiki.edg.com/pub/Wg21kona2017/StrawPolls/p0607r0.html
>
> During that work it has been found that std::ignore was not declared
> constexpr (http://cplusplus.github.io/LWG/lwg-defects.html#2773),
> which was fixed as well.

Just adding constexpr to std::ignore does ~nothing. The assignment
operator needs to be made constexpr too; there is really no other
reason to use std::ignore.