- Change all checks for APC to use the same function, for consistency

- Remove the 'title' field.
- Add the nagios hooks and all its baggage.
- Use hook_boot, and not hook_init.

- Eliminate two notices due to undefined variable.

variable used to work with D6 and earlier, we relied on it being set for us.
With 7.x, we have our own performance_query variable and settings for it.

- Use REQUEST_TIME instead of time()
- Remove wasteful SELECT COUNT(*) query, which is slow on InnoDB and PostgreSQL.