(lsh_oop_signal_callback): Return OOP_CONTINUE.
(lsh_oop_fd_read_callback): Return OOP_CONTINUE.
(lsh_oop_register_read_fd): Check want_read, so we don't try to
register the callback twice.
(lsh_oop_fd_write_callback): Fixed assertion.
(lsh_oop_fd_write_callback): Return OOP_CONTINUE.
(lsh_oop_register_write_fd): Check want_write, so we don't try to
register the callback twice.
(io_run): Print a trace message if/when oop_sys_run returns.
(do_connect_callback): Improved trace messages.
(io_connect): Initialize fd->write before calling
lsh_oop_register_write_fd.
(io_listen): Initialize fd->read before calling
lsh_oop_register_read_fd.
(close_fd): Call lsh_oop_cancel_read_fd and
lsh_oop_cancel_write_fd before clearing the alive flag.

Rev: src/io.c:1.147