daemon: UNIX domain socket for JSON-based control.

Also taken from pettycoin. 

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

daemon/jsonrpc.h

@@ -0,0 +1,47 @@
+#ifndef LIGHTNING_DAEMON_JSONRPC_H
+#define LIGHTNING_DAEMON_JSONRPC_H
+#include "config.h"
+#include "json.h"
+#include <ccan/list/list.h>
+
+struct json_connection {
+	/* The global state */
+	struct lightningd_state *state;
+
+	/* Logging for this json connection. */
+	struct log *log;
+
+	/* The buffer (required to interpret tokens). */
+	char *buffer;
+
+	/* Internal state: */
+	/* How much is already filled. */
+	size_t used;
+	/* How much has just been filled. */
+	size_t len_read;
+
+	/* We've been told to stop. */
+	bool stop;
+
+	struct list_head output;
+	const char *outbuf;
+};
+
+struct json_command {
+	const char *name;
+	char *(*dispatch)(struct json_connection *jcon,
+			  const jsmntok_t *params,
+			  struct json_result *result);
+	const char *description;
+	const char *help;
+};
+
+/* Add notification about something. */
+void json_notify(struct json_connection *jcon, const char *result);
+
+/* For initialization */
+void setup_jsonrpc(struct lightningd_state *state, const char *rpc_filename);
+
+/* Commands (from other files) */
+
+#endif /* LIGHTNING_DAEMON_JSONRPC_H */