Add more checks

The following suggestions seem useful:

* System swap activity (not used swap space)
* mysqld vsz is over 90% of the system memory

Other suggestions people have made, to be considered:

* Select_scan > 2/5 per second
* Aborted_clients > 1/2 per second
* Aborted_connects > 1/2 per second
* Select_full_join > 1/2 per second
* Slow_queries > 5/15 per second
* Table_locks_waited > 1/4 per second
* Threads_running too high
* Innodb = enabled
* Each .ibd file has a .frm file (there is a script for this in Google Code)

- tmpdir file system full.
- IO activity on the datadir file system in particular is at an elevated level.
- Slow query log is growing rapidly.
- Sort-merge-passes increasing.
- Full-joins increasing.
- Tmp-disk-tables increasing.
- Log-buffer-waits increasing.
- Aborted-clients increasing.
- Aborted-connections increasing.
- Table with range or list partitioning is about to run beyond its range, so further inserts will fail.
- Key variables on running system are not the same as variables in /etc/my.cnf. E.g. Innodb-log-file-size.
- Numerous failed login attempts.
- Numerous failed SQL privilege checks.

- ability to query app data
- replicas set readonly
- replicas writing binlog events
- replicas nearing capacity
- long-running txns
- many lock waits (or a lot of lock_wait_time)
- many queries in innodb queue
- long-lived mutex waits
- many recent fk errors
- zero-sized entries in master logs
- new entry in the error log
- system is swapping
- multiple server instances
- disk nearly full
- raid controller degraded, or dead or low battery, or battery learn cycle will start soon