Correct hash_final use across PHP versions. 

If you see this http://3v4l.org/3cF9I - the behaviour of `hash*` changed in PHP 5.2.7 and up, so we need to change how the CRCs are created in 5.2.7+

This took me a good long while to hunt down :smile: but fixes the crc in versions of PHP greater than 5.2.6.  
Currently there is no problem in 5.1.2 - 5.2.6 but any newer than that and things break - I am running 5.5.14 for instance though and the CRC's generated with the `hash*` methods are incorrect.