[ticket/12788] Update symfony components

PHPBB3-12788
[ticket/12788] Force 2.3.* on symfony dependencies

PHPBB3-12788
[ticket/12808] Fix small gap between username and drop-down arrow

PHPBB3-12808
[ticket/12816] Fix comment about logs in user_ban function

PHPBB3-12816
[ticket/12807] Changes PRUNE_FREQ to PRUNE_SHADOW_FREQ/_DAYS

PHPBB3-12807
[ticket/12807] Adds missing language variables language/en/acp/forums.php

PHPBB3-12807
[ticket/12807] New variables for _EXPLAIN

PHPBB3-12807
[ticket/12815] Show memberlist link for guests (if permitted)

PHPBB3-12815
[ticket/12815] Remove S_REGISTERED_USER for team link

PHPBB3-12815
Merge remote-tracking branch 'PayBas/ticket/12815' into develop-ascraeus

* PayBas/ticket/12815:
  [ticket/12815] Remove S_REGISTERED_USER for team link
  [ticket/12815] Show memberlist link for guests (if permitted)
Merge remote-tracking branch 'PayBas/ticket/12808' into develop-ascraeus

* PayBas/ticket/12808:
  [ticket/12808] Fix small gap between username and drop-down arrow
[ticket/12823] Remove all trailing whitespace

PHPBB3-12823
Merge remote-tracking branch 'Crizzo/ticket/12807' into develop-ascraeus
[ticket/12810] Use correct template vars for shadow pruning settings

PHPBB3-12810
Merge pull request #2699 from marc1706/ticket/12810

[ticket/12810] Use correct template vars for shadow pruning settings

* marc1706/ticket/12810:
  [ticket/12810] Use correct template vars for shadow pruning settings
[ticket/12515] Remove check for PostgreSQL 8.3+

PHPBB3-12515
Merge pull request #2654 from nickvergessen/ticket/12515

[ticket/12515] Remove check for PostgreSQL 8.3+ in search

* nickvergessen/ticket/12515:
  [ticket/12515] Remove check for PostgreSQL 8.3+
Merge pull request #2704 from hanakin/ticket/12823

[ticket/12823] Remove all trailing whitespace

* hanakin/ticket/12823:
  [ticket/12823] Remove all trailing whitespace
Merge pull request #2679 from dhruvgoel92/ticket/12788

[ticket/12788] Update symfony components

* dhruvgoel92/ticket/12788:
  [ticket/12788] Force 2.3.* on symfony dependencies
  [ticket/12788] Update symfony components
Merge pull request #2697 from n-aleha/ticket/12816

[ticket/12816] Fix comment about logs in user_ban function

* n-aleha/ticket/12816:
  [ticket/12816] Fix comment about logs in user_ban function