Add eventlog/trace stuff for capabilities: create/delete/enable/disable
Now that we can adjust the number of capabilities on the fly, we need this reflected in the eventlog. Previously the eventlog had a single startup event that declared a static number of capabilities. Obviously that's no good anymore. For compatability we're keeping the EVENT_STARTUP but adding new EVENT_CAP_CREATE/DELETE. The EVENT_CAP_DELETE is actually just the old EVENT_SHUTDOWN but renamed and extended (using the existing mechanism to extend eventlog events in a compatible way). So we now emit both EVENT_STARTUP and EVENT_CAP_CREATE. One day we will drop EVENT_STARTUP. Since reducing the number of capabilities at runtime does not really delete them, it just disables them, then we also have new events for disable/enable. The old EVENT_SHUTDOWN was in the scheduler class of events. The new EVENT_CAP_* events are in the unconditional class, along with the EVENT_CAPSET_* ones. Knowing when capabilities are created and deleted is crucial to making sense of eventlogs, you always want those events. In any case, they're extremely low volume.