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)
diff --git a/src/version.c b/src/version.c
index 1adac5a..6644ac4 100644
--- a/src/version.c
+++ b/src/version.c
@@ -704,6 +704,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    480,
+/**/
     479,
 /**/
     478,