r5185: make all the events data structures private to events.c. This will

r5185: make all the events data structures private to events.c. This will
make it possible to add optimisations to the events code such as
keeping the next timed event in a sorted list, and using epoll for
file descriptor events.

I also removed the loop events code, as it wasn't being used anywhere,
and changed timed events to always be one-shot (as adding a new timed
event in the event handler is so easy to do if needed)
(This used to be commit d7b4b6de51342a65bf46fce772d313f92f8d73d3)