Apply WordPress latest changes to phpass class

Copied from 6.7.1 [1].

[1]: https://github.com/WordPress/WordPress/blob/6.7.1/wp-includes/class-phpass.php

Add WordPress password hashing framework

Copied from WordPress 4.3.1
httphttpss://github.com/WordPress/WordPress/blob/4.3.1/wp-includes/class-phpass.php