login_check_processing.php: simplify checks
login_check_processing.php: simplify checks

We can avoid extra database work by using the `last_login`
information that we already loaded into the `SmrAccount`.

This also makes the checks independent of the structure of
the `account` table.

hemberger/smr,hemberger/smr,smrealms/smr,smrealms/smr,smrealms/smr,hemberger/smr,hemberger/smr