[ticket/develop/10772] Unit tests for forum specific style

Unit tests for forum specific style for 3.1 branch

PHPBB3-10772
Merge branch 'ticket/10772' into ticket/develop/10772

* ticket/10772:
  [ticket/10772] Use forum specific style for trigger_error
[ticket/develop/10772] Fix copyright year

PHPBB3-10772
[feature/twig] Adding Twig dependency to composer.json

PHPBB3-11598
[feature/twig] WIP extension/lexer/some tokenparsers/nodes

PHPBB3-11598
[feature/twig] Support our old INCLUDE statements (no quotes)

Better code for handling IF .blah

PHPBB3-11598
[feature/twig] Working on DEFINE

PHPBB3-11598
[feature/twig] More work on the lexer

Committing what I have now to save it as I'm trying another method next

PHPBB3-11598
[feature/twig] Replace phpBB template code with Twig syntax, then parse w/Twig

Fixing begin token/node, adding includejs token/node

PHPBB3-11598
[feature/twig] BEGIN loops now work

PHPBB3-11598
[feature/twig] Replace phpBB template with Twig

Move phpbb_template class to phpbb_template_phpbb
Changed phpbb_template class to an interface
Switch services.yml to load phpbb_template_twig instead of phpbb_template

PHPBB3-11598
[feature/twig] Language output assignments, using context class again

PHPBB3-11598
[feature/twig] Update composer.lock

PHPBB3-11598
[feature/twig] Fixing IF .blah correctly

PHPBB3-11598
[feature/twig] Correcting output of INCLUDEJS

PHPBB3-11598
[feature/twig] Some additional operators, more stuff for IF

PHPBB3-11598
[feature/twig] Use phpBB's resource locator to find templates

PHPBB3-11598
[feature/twig] Use phpbb_template_twig in tests

Replace all new phpbb_template( with new phpbb_template_twig(

PHPBB3-11598
[feature/twig] Use twig loader filesystem with namespaces to add paths

Twig now handles loading style files on its own

PHPBB3-11598
[feature/twig] Fix improper template syntax in acp_forums.html

PHPBB3-11598