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

PHPBB3-12836
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
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12836] Add event core.functions.redirect