Synchronizes adding an error to the error queue, and checks if the error queue is too long - if so, we drop the error on the floor after logging a warning.

Get the errors currently queued up. Unsent errors are left over from a previous unsuccessful attempt to send them to the server.

*Use sparingly for difficult to track bugs.*

Track internal agent errors for communication back to New Relic. To use, make a specific subclass of NewRelic::Agent::InternalAgentError, then pass an instance of it to this method when your problem occurs.

Limits are treated differently for these errors. We only gather one per class per harvest, disregarding (and not impacting) the app error queue limit.

checks the size of the error queue to make sure we are under the maximum limit, and logs a warning if we are over the limit.