Add lost event count in API
Add an option to babeltrace API to know how many events were lost.
When opening a trace with babeltrace that contains lost events, messages like the following indicate that events were lost during the recording.
[warning] Tracer discarded 45759 events between [14:14:00.327341608] and [14:14:00.327341813]. You should consider recording a new trace with larger buffers or with fewer events enabled.
It would be interesting to have similar information when using the babeltrace API to read a trace.