badwords: catch and fix threading-related words

Also:
- sync newlines between the two threaded examples.

Closes #20001

docs/examples/http2-upload.c

@@ -161,7 +161,7 @@ static int my_trace(CURL *curl, curl_infotype type,
     known_offset = 1;
   }
   secs = epoch_offset + tv.tv_sec;
-  now = localtime(&secs);  /* not thread safe but we do not care */
+  now = localtime(&secs);  /* not thread-safe but we do not care */
   snprintf(timebuf, sizeof(timebuf), "%02d:%02d:%02d.%06ld",
            now->tm_hour, now->tm_min, now->tm_sec, (long)tv.tv_usec);