[feature/auth-refactor] Refactor acp_board for new auth interface

Partially refactors acp_board for the new authentication interface.
Leaves some questionable if statements in the file.
Modifies the interface to correctly impletment the acp() method.
Modifies each provider to comply with the above mentioned interface
modification.

PHPBB3-9734

phpBB/includes/auth/provider_apache.php

@@ -258,7 +258,7 @@ class phpbb_auth_provider_apache implements phpbb_auth_provider_interface
 		return false;
 	}
 
-	public function acp()
+	public function acp($new)
 	{
 		return;
 	}