pgsql: Fix for C++ compatibility

Fix for C++ compatibility

After commit 476b35d4e31, some buildfarm members are complaining about
not recognizing _Noreturn when building the new C++ module
test_cplusplusext. This is not a C++ feature, but it was gated like

#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
#define pg_noreturn _Noreturn

But apparently that was not sufficient. Some platforms define
__STDC_VERSION__ even in C++ mode. (In this particular case, it was
g++ on Solaris, but apparently this is also done by some other
platforms, and it is allowed by the C++ standard.) To fix, add a

... && !defined(__cplusplus)

Reviewed-by: Andres Freund <andres(at)anarazel(dot)de>
Discussion: https://www.postgresql.org/message-id/flat/CAGECzQR21OnnKiZO_1rLWO0-16kg1JBxnVq-wymYW0-_1cUNtg(at)mail(dot)gmail(dot)com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b4555cb070f134c04328df54ce31d4ef1970f3bb

Modified Files
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src/include/c.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)