Merge branch 'ticket/13138-2' into ticket/13138-asc

Conflicts:
	phpBB/phpbb/session.php
[ticket/13138] Fix the session key tests

PHPBB3-13138
[ticket/13138] Type hint the variables for IDE usage

PHPBB3-13138
Merge pull request #3040 from nickvergessen/ticket/13138-asc

[3.1] Ticket/13138 Only use cookie data when we do not force a user_id

Conflicts:
	phpBB/phpbb/session.php