Support disconnected tracing.

	Support disconnected tracing.
	* infcmd.c (detach_command): Ask whether to stop tracing.
	* cli/cli-cmds.c (quit_command): Ditto.
	* breakpoint.h (struct breakpoint): New field number_on_target.
	* breakpoint.c (create_tracepoint_from_upload): New function.
	(get_tracepoint_by_number_on_target): New function.
	* remote.c (struct remote): New field disconnected_tracing.
	(remote_disconnected_tracing_feature): New function.
	(remote_protocol_features): Add DisconnectedTracing.
	(struct uploaded_tp): New struct.
	(uploaded_tps): New global.
	(get_uploaded_tp): New function.
	(find_matching_tracepoint): New function.
	(remote_get_tracing_state): New function.
	(remote_start_remote): Call it.
	* tracepoint.c (disconnected_tracing): New global.
	(trace_start_command): Initialize number_on_target.
	(stop_tracing): New function, split out from...
	(trace_stop_command): Call stop_tracing.
	(get_trace_status): New function, split out from...
	(trace_status_command): Call get_trace_status, add info on
	disconnection behavior.
	(disconnect_or_stop_tracing): New function.
	(finish_tfind_command): Translate from number on target.
	(trace_find_tracepoint_command): Translate to number on target.
	(send_disconnected_tracing_value): New function.
	(set_disconnected_tracing): New function.
	(_initialize_tracepoint): Add disconnected-tracing variable.
	* NEWS: Mention disconnected tracing.

	* gdb.texinfo (Starting and Stopping Trace Experiments): Document
	disconnected tracing.
	(Tracepoint Packets): Document new protocol.