lightningd: list disabled plugins in listconfig.

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

lightningd/plugin.h

@@ -274,6 +274,12 @@ void json_add_opt_plugins(struct json_stream *response,
 			  const struct plugins *plugins);
 
 
+/**
+ * Add the disable-plugins options to listconfigs.
+ */
+void json_add_opt_disable_plugins(struct json_stream *response,
+				  const struct plugins *plugins);
+
 /**
  * Used by db hooks which can't have any other I/O while talking to plugin.
  *