patch 8.2.0553: error for unused argument

Problem:    Error for unused argument.
Solution:   Add UNUSED.

src/libvterm/t/harness.c

@@ -65,7 +65,7 @@ static VTermScreen *screen;
 
 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;
 

src/version.c

@@ -738,6 +738,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    553,
 /**/
     552,
 /**/