(handle_channel_success, handle_channel_failure):

Use the command_context associated with the request, if it's
non-NULL.
(format_channel_request_i): Deleted function.
(channel_send_request): Changed arguments to include a want_reply
flag and a struct command_context *.

Rev: src/channel.c:1.125.2.22
Rev: src/channel.h:1.77.2.17