patch 9.0.0480: cannot use a :def varargs function with substitute()

Problem:    Cannot use a :def varargs function with substitute().
Solution:   Use has_varargs(). (closes #11146)

src/version.c

@@ -703,6 +703,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    480,
 /**/
     479,
 /**/