kconfig: Do not print status messages in make -s mode

Add an -s option to the various frontends and pass it when make -s is
used. Also, use $(kecho) instead of @echo in the Makefile.

Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/kconfig/nconf.c

@@ -1482,6 +1482,11 @@ int main(int ac, char **av)
 	bindtextdomain(PACKAGE, LOCALEDIR);
 	textdomain(PACKAGE);
 
+	if (ac > 1 && strcmp(av[1], "-s") == 0) {
+		/* Silence conf_read() until the real callback is set up */
+		conf_set_message_callback(NULL);
+		av++;
+	}
 	conf_parse(av[1]);
 	conf_read(NULL);