(make_global_request_status): New function.
(global_request_response): New class.
(do_global_request_response): New function.
(make_global_request_response): New function.
(do_global_request): Pass a callback object to the handler.

* src/channel.h (channel_table): New attributes
active_global_requests and pending_global_requests.
(global_request_callback): New class.
(global_request): Let the handler method take a
global_request_callback as argument.

Rev: src/channel.c:1.39
Rev: src/channel.h:1.33