R1:ba956711a56b

Change password_hash() algorithm from CRYPT_BLOWFISH to PASSWORD_BCRYPT.

Summary:
PHP 5.5 specifies constant PASSWORD_BCRYPT should be used in password_hash()
instead of CRYPT_BLOWFISH. Using CRYPT_BLOWFISH is not supported in either PHP
or HHVM. This constant breaks Username / Password authentication.

Test Plan:
Login using Username/Password with bcrypt hash. Before applying the patch,
No matter what password entered, it will always fail authentication. After this
patch, user should be able to login…