(lsh_oop_register_callout): New function.
(lsh_oop_cancel_callout): New function.
(do_kill_callout): New function.
(io_callout): Deleted delay argument, as delays are not currently
implemented.

* src/io.c (io_final): Call gc_final. That makes sure that all
callbacks are cancelled. Updated callers to not use gc_final, only
io_final.

Rev: src/io.c:1.150
Rev: src/io.h:1.81