use.
(register_channel): New argument take_into_use.
(lookup_channel_reserved): New function that returns channels that
are marked as reserved, but not in use.
(do_channel_open_continue): Call register_channel with
take_in_use=1.
(do_channel_open_confirm): Use lookup_channel_reserved(). Call
use_channel().
(do_channel_open_failure): Use lookup_channel_reserved().
(format_channel_open): Renamed from prepare_channel_open. Don't
call alloc_channel() or register_channel().

* src/channel.h (CHANNEL_FREE, CHANNEL_RESERVED, CHANNEL_IN_USE):
New three-level classification for the in_use table.

* src/channel.c (exc_finish_channel_handler): Use pointer to
connection rather than to its channel table.

Rev: src/channel.c:1.71
Rev: src/channel.h:1.51