linux: always deregister closing fds from epoll

If the same file description is open in two different processes, then
closing the file descriptor is not sufficient to deregister it from the
epoll instance (as described in epoll(7)), resulting in spurious events
that cause the event loop to spin repeatedly. So always explicitly
deregister it.

Fixes #1099.

Conflicts:
	test/test-spawn.c
kqueue: invalidate fd in uv_fs_event_t

Invalidate file descriptor when closing `uv_fs_event_t` handle. Note
that `uv__io_stop` is just removing `fd` from `loop->watchers` and not
actually invalidating all consequent events in a `kevent()` results.

fix joyent/node#1101
Merge branch 'v0.10'

Conflicts:
	test/test-spawn.c