[ticket/12809] Fix select button and dropdown list items in RTL.

PHPBB3-12809
[ticket/12809] Remove obsolete rules and selector.

PHPBB3-12809
[ticket/12809] Restore text-align for the pagination.

PHPBB3-12809
[ticket/12822] Remove "None" option from avatar select boxes

This option is just used for deleting avatars for which we already have
a checkbox.

PHPBB3-12822
[ticket/12822] Add method for deleting avatars and use confirm_box

The method will take care of the actual deletion process in the avatar manager.
Additionally, we'll be using a confirm box while deleting the avatar to prevent
users from accidentally deleting their avatars.

PHPBB3-12822
[ticket/12822] Fix test runs of avatar manager_test

PHPBB3-12822
[ticket/12931] Fix general error on user registration

Fix "Illegal use of $_SERVER" general error on user registration
when $config['server_name'] is not set.

PHPBB3-12931
[ticket/12964] Correct use of undefined $row variable.

PHPBB3-12964
Merge pull request #2714 from prototech/ticket/12809

[ticket/12809] Fix select button and dropdown list items in RTL.
Merge branch 'develop-ascraeus' into develop
Merge pull request #2864 from rxu/ticket/12931

[ticket/12931] Fix general error on user registration
Merge branch 'develop-ascraeus' into develop
Merge pull request #2866 from bantu/ticket/12964

[ticket/12964] Correct use of undefined $row variable.
Merge branch 'develop-ascraeus' into develop

# By Andreas Fischer
# Via Andreas Fischer (1) and Dhruv Goel (1)
* develop-ascraeus:
  [ticket/12964] Correct use of undefined $row variable.
[ticket/12942] Add core.add_form_key core event

Add core.add_form_key core event to allow extensions modifying
form key.

PHPBB3-12942
[ticket/12967] Fix undefined variable phpbb_dispatcher error.

PHPBB3-12967
[ticket/12944] Add core.login_forum_box core event

Add core.login_forum_box core event to allow extensions
performing additional actions on forum login.

PHPBB3-12944
[ticket/11854] Move captcha stuff to phpbb/ and use DI for plugins

PHPBB3-11854
[ticket/11854] Add a migration to update the captcha_plugin setting

PHPBB3-11854
[ticket/11854] Add missing dot in the migration file

PHPBB3-11854