[ticket/12788] Update symfony components

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

PHPBB3-12788
[ticket/12816] Fix comment about logs in user_ban function

PHPBB3-12816
[ticket/12823] Remove all trailing whitespace

PHPBB3-12823
[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