patch 9.0.0511: unnecessary scrolling for message of only one line

Problem:    Unnecessary scrolling for message of only one line.
Solution:   Only set msg_scroll when needed. (closes #11178)
diff --git a/src/version.c b/src/version.c
index d7d5bd3..c6f76ac 100644
--- a/src/version.c
+++ b/src/version.c
@@ -700,6 +700,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    511,
+/**/
     510,
 /**/
     509,