Updated libubox to 2020

Makefile

 all:
 	tar xf libubox.tar.xz
-	patch -Np1 -d libubox < libubox-is_error.patch
 	cd libubox && cmake CMakeLists.txt -DBUILD_LUA=OFF -DCMAKE_INSTALL_PREFIX=/usr
 	$(MAKE) -C libubox
 	$(MAKE) -C libubox install

libubox-is_error.patch

-diff -uNr a/blobmsg_json.c b/blobmsg_json.c
---- a/blobmsg_json.c	2017-09-06 21:50:00.000000000 +0000
-+++ b/blobmsg_json.c	2017-09-08 17:57:48.641862452 +0000
-@@ -75,7 +75,7 @@
- {
- 	bool ret = false;
- 
--	if (is_error(obj))
-+	if (obj == NULL)
- 		return false;
- 
- 	if (json_object_get_type(obj) != json_type_object)
-diff -uNr a/jshn.c b/jshn.c
---- a/jshn.c	2017-09-06 21:50:00.000000000 +0000
-+++ b/jshn.c	2017-09-08 17:58:01.131381844 +0000
-@@ -159,7 +159,7 @@
- 	json_object *obj;
- 
- 	obj = json_tokener_parse(str);
--	if (is_error(obj) || json_object_get_type(obj) != json_type_object) {
-+	if (obj == NULL || json_object_get_type(obj) != json_type_object) {
- 		fprintf(stderr, "Failed to parse message data\n");
- 		return 1;
- 	}