TT#88951 abstractise CLI handling and writing

Change-Id: I004cbc4a8690b11822ab54f34af01557b87c6a02

include/cli.h

@@ -13,6 +13,15 @@ struct cli {
    struct streambuf_listener listeners[2];
 };
 
+struct cli_writer;
+
+struct cli_writer {
+	void (*cw_printf)(struct cli_writer *, const char *, ...) __attribute__ ((format (printf, 2, 3)));
+	void *ptr;
+};
+
 struct cli *cli_new(struct poller *p, endpoint_t *);
 
+void cli_handle(str *instr, struct cli_writer *);
+
 #endif /* CLI_UDP_H_ */