[task/code-sniffer] Add PSR1.Files.SideEffects.FoundWithSymbols

PHPBB3-11980
[task/code-sniffer] Remove the IN_PHPBB check side-effect from class files.

PHPBB3-11980
[task/code-sniffer] Replace spaces with tabs.

PHPBB3-11980
[task/code-sniffer] Completely ignore database_update.php.

PHPBB3-11980