libstdc++ PATCH to harmonize noexcept

[Jonathan Wakely]

On 14/11/17 13:56 -0500, Jason Merrill wrote:
>While working on an unrelated issue I noticed that the compiler didn't
>like some of these declarations after preprocessing, when they aren't
>protected by system-header permissiveness.
>
>I thought about limiting the permissiveness to only extern "C"
>functions, but I believe that system headers are adding more C++
>declarations, so we'd likely run into this issue again.
>
>Shouldn't we build libstdc++ with -Wsystem-headers?  Maybe along with
>-Wno-error=system-headers?

It's been suggested before:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=50871