There are undocumented functions:
event_timer_new() alias of event_new()
event_timer_set(event, callback, args)
event_timer_pending(event, timeout)
event_timer_add() alias of event_add()
event_timer_del() alias of event_del()
There are undocumented constants:
EVBUFFER_READ (1)
EVBUFFER_WRITE (2)
EVBUFFER_EOF (16)
EVBUFFER_ERROR (32)
EVBUFFER_TIMEOUT (64)
These flags - second argument in buffer's error-callback