[ticket/12756] Fix mysqli_fetch_assoc on hhvm

PHPBB3-12756
Merge pull request #2634 from Nicofuma/ticket/12756

[ticket/12756] Fix mysqli_fetch_assoc on hhvm

* Nicofuma/ticket/12756:
  [ticket/12756] Fix mysqli_fetch_assoc on hhvm
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12756] Fix mysqli_fetch_assoc on hhvm