These use the recently extracted `phc` crate (#761)

Releases the following:
- `argon2` v0.6.0-rc.4
- `balloon-hash` v0.5.0-rc.2
- `password-auth` v1.1.0-pre.3
- `pbkdf2` v0.13.0-rc.4
- `scrypt` v0.12.0-rc.5