kernel - Fix read event on file for select/poll API
* select/poll have always returned an immediate read event on regular
files, but kqueue is expected to only return a EVFILT_READ event
when not sitting at the file EOF.
* The kernel adds a NOTE_OLDAPI flag which filter functions can use to
discern between select/poll and kqueue related knotes.
* Adjust filesystem filter function to always return an immediate
event for reads via select/poll.
* Fixes guile, which for some reason beyond our ken select()'s for a
read event on a file.
Reported-by: Johannes Hofmann <johannes.hofmann@gmx.de>