[ticket/12901] Fix type hinting of style $level

PHPBB3-12901
[ticket/12901] Fix another wrong type hint for $level

PHPBB3-12901
[ticket/12836] Add event core.functions.redirect

PHPBB3-12836
[ticket/12875] Find language files in the default and english language ...

... when looking for info_xcp_ files.

PHPBB3-12875
Merge pull request #2807 from nickvergessen/ticket/12875

[ticket/12875] Find language files in the default and english language
Merge pull request #2799 from nickvergessen/ticket/12901

Ticket/12901 Wrong type hint in show_available_child_styles() doc block
Merge pull request #2717 from Nicofuma/ticket/12836

[ticket/12836] Add event core.functions.redirect

* Nicofuma/ticket/12836:
  [ticket/12836] Add event core.functions.redirect