continuation and exception handler attributes with a
channel_open_info.
(tcpforward_connect_done): Replaced COMMAND_CONTINUATION call with
calls to channel_open_confirm and channel_forward_start_io.
(tcpforward_connect_error): Replaced EXCEPTION_RAISE call with a
call to channel_open_deny.
(tcpforward_connect): Take a channel_open_info as argument.
Adapted to new CHANNEL_OPEN convention.

Rev: src/tcpforward.c:1.71
Rev: src/tcpforward.h:1.22