Given PASSWORD EXPIRE and PASSWORD EXPIRE [NEVER|INTERVAL x DAY] are
two different mechanisms, SHOW CREATE USER should display all the
information required to restore the state of an account which
includes both a manual expired state and an automatic policy.

The solution proposed here keeps a CREATE USER ... PASSWORD EXPIRE
statement and adds an aditional
ALTER USER .. PASSWORD EXPIRE [NEVER|INTERVAL x DAY] when necessary

This way a tool can restore almost the complete state of an account
as it was before a dump. The only information left still is the
value of the password_last_changed column from mysql.global_priv