patch 8.2.0553: error for unused argument

Problem:    Error for unused argument.
Solution:   Add UNUSED.
diff --git a/src/libvterm/t/harness.c b/src/libvterm/t/harness.c
index 5fa4cfb..75869d7 100644
--- a/src/libvterm/t/harness.c
+++ b/src/libvterm/t/harness.c
@@ -65,7 +65,7 @@
 
 static VTermEncodingInstance encoding;
 
-static void term_output(const char *s, size_t len, void *user)
+static void term_output(const char *s, size_t len, void *user UNUSED)
 {
   size_t i;
 
diff --git a/src/version.c b/src/version.c
index 2985dd0..a9cdd6a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -739,6 +739,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    553,
+/**/
     552,
 /**/
     551,