Lock out authentication if the account has been locked by pw(8).

Lock out authentication if the account has been locked by pw(8).

In account management, verify whether the account has been locked
with `pw lock', so that it's impossible to log into a locked account
using an alternative authentication mechanism, such as an ssh key.
This change affects only accounts locked with pw(8), i.e., having a
`*LOCKED*' prefix in their password hash field, so people still can
use a different pattern to disable password authentication only.

Also, clean out some (void) casts and use libypclnt.

Obtained-from: FreeBSD