This statement does not serve a purpose anymore.
In a long forgotten world it indicated the main version number of PHP which the code in the file was compatible to.
http://pear.php.net/manual/en/standards.sample.php
But since PHP 5.1 and later this is only marginally true.
Thus I propose to remove it from CakePHP.
When encoded values are present in header fields, they need to have
newlines removed as leaving the newlines in place and interfere with
delivery on Qmail based SMTP servers.
Fixes#2209