[PATCH] libstdc++: Apply proposed resolution for LWG 3449 [PR95322]

[Jonathan Wakely]

On 12/10/20 10:19 -0400, Patrick Palka via Libstdc++ wrote:
>Now that the frontend bug PR96805 is fixed, we can apply the proposed
>resolution for this issue.
>
>This slightly deviates from the proposed resolution by declaring _CI a
>member of take_view instead of take_view::_Sentinel, since it doesn't
>depend on anything within _Sentinel anymore.
>
>Tested on x86_64-pc-linux-gnu, does this look OK for trunk?

OK, thanks.