- the intention for my_getevents syscall is now better explained,
why are we using it (to be able to interrupt io_getevents syscall via
io_destroy()).

- Fix comment for MAX_EVENTS in getevent_thread_routine.
MAX_EVENTS is more of less arbitrary constant, chosen such that events array
is big enough to get multiple simultaneous io completions, but small
enough so it does not blow the thread's stack.