Add os_alert.c skeleton.
Add pattern matching capability to os_alert.c
Constructors for os_alert.c

Add the alert_criteria_constructor_t, alert_action_constructor_t,
alert_criteria_t, alert_t, and alert_event_t data types.
Add data structures to store alerts.
Reorganize.
Add alert notice action.
Added subcommands. Added node deletion.
Add nick criteria.
os_alert commands take the correct number of args.

Use sstrdup() when copying out of args for persistent data.

Add error checking os_cmd_alert_add.
The alert tree is simplified.

The nodes point to the alert and not its node in the list.
Alerts indexed from 1
Fix pattern_match. match returns 0 on success.
Alerts can now trigger on connect.
Add support for nick change events.