fix C++ builds broken by cdc4a174060

fix C++ builds broken by cdc4a174060

In commit cdc4a174060 static noreturn function, on a C++ build, (specific
example, GCC ) got a post preprocessor prototype of
"extern "C" static void S_fn_doesnt_return(". GCC generates a compile error
if "extern "C"" and static used together. Plain C build were not affected.

This commit fixed the problem by creating 2 new static exclusive macros, so
extern "C" does not wind up on statics in a C++ build. The macros allow
enough flexibility so any compiler/platform that needs a noreturn
declaration specifier instead of a noreturn function attribute can have
one.