BUG/MEDIUM: kqueue: When adding new events, provide an output to get errors.

BUG/MEDIUM: kqueue: When adding new events, provide an output to get errors.

When adding new events using kevent(), if there's an error, because we're
trying to delete an event that wasn't there, or because the fd has already
been closed, kevent() will either add an event in the eventlist array if
there's enough room for it, and keep on handling other events, or stop and
return -1.
We want it to process all the events, so give it a large-enough array to
store any error.

Special thanks to PiBa-NL for diagnosing the root cause of this bug.

This should be backported to 1.8.