basic/macros: rename noreturn into _noreturn_ (#8456)

"noreturn" is reserved and can be used in other header files we include:

  [   16s] In file included from /usr/include/gcrypt.h:30:0,
  [   16s]                  from ../src/journal/journal-file.h:26,
  [   16s]                  from ../src/journal/journal-vacuum.c:31:
  [   16s] /usr/include/gpg-error.h:1544:46: error: expected ‘,’ or ‘;’ before ‘)’ token
  [   16s]  void gpgrt_log_bug (const char *fmt, ...)    GPGRT_ATTR_NR_PRINTF(1,2);

Here we include grcrypt.h (which in turns include gpg-error.h) *after* we
"noreturn" was defined in macro.h.

src/basic/log.c

@@ -814,7 +814,7 @@ static void log_assert(
         log_dispatch_internal(level, 0, file, line, func, NULL, NULL, NULL, NULL, buffer);
 }
 
-noreturn void log_assert_failed_realm(
+_noreturn_ void log_assert_failed_realm(
                 LogRealm realm,
                 const char *text,
                 const char *file,
@@ -826,7 +826,7 @@ noreturn void log_assert_failed_realm(
         abort();
 }
 
-noreturn void log_assert_failed_unreachable_realm(
+_noreturn_ void log_assert_failed_unreachable_realm(
                 LogRealm realm,
                 const char *text,
                 const char *file,