At [L72-L76](https://github.com/phpbb/phpbb/blob/develop-ascraeus/phpBB/includes/diff/engine.php#L72-#L76) it seems that:
1. `\r\n => \n`
2. `\r => \n`

So maybe reword this to:
If true, firsth `\r\n` and then `\r` are replaced by `\n`?