Update the password FAQ: drop hash() references, add password_*() instead.

I've also expanded on storing passwords and salt generation. This could use a
review from someone else who feels qualified to opine on password security.


git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@332642 c90b9560-bf6c-de11-be94-00142212c4b1