Initial commit of  the decrypt function for PHP
Create a new decrypt_data function for the RNCryptor and change the name of the origin decrypt_data() function to CPCryptController_decrypt_data().
Add example codes example for the decrypt_data() function.
Create crypt-common.inc file and put the hash_pbkdf2() function in it as we use the hash_pbkdf2()function in both enccrypt.php and decrypt.php.
Merge pull request #56 from guysung/master

decrypt.php initial implementation.