[ticket/11405] Fix "only variables should be passed by reference"

PHPBB3-11405
[ticket/11405] Add unit tests for post_in_queue

PHPBB3-11405
[ticket/11405] Check read permission before sending *_in_queue notifications

PHPBB3-11405
[ticket/11405] Clarify comment with "global" and forum_id = 0

Forum ID 0 in permission checks, checks the global moderator permission.

PHPBB3-11405