Hash: add sha256-96 and sha512-96

IPSec uses them and some versions of OpenSSH use them (even though RFC6668 makes no mention of them)
Could you elaborate on your suggestion? php.net suggests [method overloading](http://php.net/manual/en/language.oop5.overloading.php) makes use of `__call` or `__callStatic`, although the latter would break the 5.2 unit tests as `__callStatic` was introduced in PHP 5.3. And even if that's what you meant it is unclear to me how you're envisioning those be used.

None-the-less, the unit tests work as of the latest commit.