Removed "PHP 5" from file header DocBlocks

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.
Merge pull request #2319 from ravage84/php-5-removal

Removed "PHP 5" from file header DocBlocks