Some compilers define __STDC_VERSION__ in c++

Some compilers define __STDC_VERSION__ in c++

Some compilers(g++ on Solaris/Illumos) define __STDC__VERSION__ in c++ .
This causes c++ code that uses openssl to break on these compilers since
_Noreturn is not a keyword in c++ .

CLA: trivial

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/14944)

(cherry picked from commit 1f3b58d8413cfa3824e9c0a146dee6ceedbc367e)