There is typically one such base for each thread which needs
to process events. The poll base is created by ul_evpoll_new
call. ul_evpoll_destroy informs all attached triggers (UL_EVP_DONE),
about base cease, ensures, that implementation specific data
are released even for triggers, which do not call ul_evptrig_done /
handle UL_EVP_DONE, closes and deallocates base.
The call ul_evpoll_dispatch starts single iteration waiting
for events. If there is no need to implement own loop in application
the ul_evpoll_loop can be called to handle all events for given thread.
The loop is terminated when call ul_evpoll_quilt_loop is used
during iteration.