[ticket/12913] Add more parameters to core.submit_post_end event

As @event core.modify_submit_post_data can modify any of the
function submit_post parameters, they may be needed to perform
actions directly after a post or topic has been submitted in
@event core.submit_post_end (includes/functions_posting.php).

PHPBB3-12913
Merge pull request #2806 from rxu/ticket/12913

[ticket/12913] Add more parameters to core.submit_post_end event

* rxu/ticket/12913:
  [ticket/12913] Add more parameters to core.submit_post_end event