[ticket/12880] core.mcp_queue_!is_topics_query_before

Adding core.mcp_queue_!is_topics_query_before

https://tracker.phpbb.com/browse/PHPBB3-12880

PHPBB3-12880
@marc1706 OK. Fine by me. I just see the other as quicker to read.

@nickvergessen That is wrong. `$topic_id` is always set and not NULL. That's what the code "says"