agent: Send PROGRESS status lines to the client.
* agent/gpg-agent.c (struct progress_dispatch_s): New. (progress_dispatch_list): New. (main): Register libgcrypt pogress handler. (agent_libgcrypt_progress_cb): New. (agent_set_progress_cb): New. (unregister_progress_cb): New. (agent_deinit_default_ctrl): Call unregister. * agent/command.c (progress_cb): New. (start_command_handler): Register progress callback.
- Signed-off-by: Werner Koch <wk@gnupg.org>