Deleted channel_success and channel_failure.
(do_channel_success): Use pending_requests queue rather than
channel_success and channel_failure.
(do_channel_failure): Likewise.

* src/channel.h (ssh_channel): New attribute pending_requests
(a queue). Removed methods channel_success and channel_failure.

Rev: src/channel.c:1.34
Rev: src/channel.h:1.30