[ticket/11881] Timezone migration can take a long time

PHPBB3-11881
[ticket/11881] Better split the timezone conversion into chunks; add test

PHPBB3-11881
[ticket/11881] Make sure user_timezone isn't converted twice

PHPBB3-11881
[ticket/11881] Limit to 500

PHPBB3-11881
[ticket/11881] Fix test filename

PHPBB3-11881
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12293] Add missing compact() call to phpBB/phpbb/log/log.php events.
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12292] Improve style details page
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/11357] Correcting invalid markup
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/11904] Update explanation for what Allow CDN does
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12035] Correcting the condition
  [ticket/12035] Adding necessary conditions
  [ticket/12035] Adding link to user posts to ACP page
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12289] Add viewtopic template events for posts specific custom notices
Merge branch 'develop-ascraeus' into develop

# By Joas Schilling
# Via Dhruv (1) and Joas Schilling (1)
* develop-ascraeus:
  [ticket/12268] Do not use substr but just compare the character
  [ticket/12268] Rename class file to recursive_dot_prefix_filter_iterator.php
  [ticket/12268] Move class out of extension namespace and rename it
  [ticket/12268] Do not search in folders starting with a dot
  [ticket/12268] Use FilesystemIterator::SKIP_DOTS
  [ticket/12268] Extension finder should not crawl through .git/ of extensions
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12292] Fix syntax error in admin.css
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12297] Delete user_from column on update
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/10174] Rename "Ban usernames" to "Ban users" in ACP
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12302] Added `--no-dev` to composer call in build.xml
  [ticket/12302] Updated composer.phar to 1.0.0-alpha8
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12310] Don't autocomplete SMTP user/pass on install
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12257] Use MyISAM in PHP 5.3 environment such that FULLTEXT tests run.
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/11360] Updating default value of $display_online_list
  [ticket/11360] Avoiding online list where not required
  [ticket/11360] Change second parameter in page_header function
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/11230] Add missing last returns to dock block
  [ticket/11230] Update cache driver dock blocks
  [ticket/11230] Use inheritdoc in docblocks in cache drivers