inotify: rewrite inotify-kernel

Remove the hardwired 1 second event queue logic from inotify-kernel and
replace it with something vastly less complicated.

Events are now reported as soon as is possible instead of after a
delay.

We still must delay IN_MOVED_FROM events in order to look for the
matching IN_MOVED_TO events, and since we want to report events in order
this means that events behind those events can also be delayed.  We
limit ourselves, however:

 - no more than 100 events can be delayed at a time

 - no event can be delayed by more than 10ms

https://bugzilla.gnome.org/show_bug.cgi?id=627285