[ticket/11981] Fix code sniffer complaints

PHPBB3-11981
Merge remote-tracking branch 'marc1706/ticket/11981' into develop

* marc1706/ticket/11981:
  [ticket/11981] Fix code sniffer complaints
[task/code-sniffer] Require code sniffer to pass on Travis CI.

PHPBB3-11980
[task/code-sniffer] Check phpBB/phpbb first. This is where new files go.

PHPBB3-11980
[task/code-sniffer] Reorganise .travis.yml

PHPBB3-11980
[task/code-sniffer] Cleanup code sniffer ruleset files.

PHPBB3-11980
Merge pull request #1835 from bantu/task/code-sniffer

[task/code-sniffer] Require PHP Code Sniffer to pass
[ticket/11986] Fix undefined index: poster_id in file.php.

PHPBB3-11986
Merge remote-tracking branch 'prototech/ticket/11986' into develop

* prototech/ticket/11986:
  [ticket/11986] Fix undefined index: poster_id in file.php.