patch 9.0.0257: "->" in ":scriptnames" output not tested yet

Problem:    "->" in ":scriptnames" output not tested yet.
Solution:   Add a check.
diff --git a/src/version.c b/src/version.c
index ec2f360..c46894d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -732,6 +732,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    257,
+/**/
     256,
 /**/
     255,