updated for version 7.4.597
Problem:    Cannot change the result of systemlist().
Solution:   Initialize v_lock. (Yukihiro Nakadaira)
diff --git a/src/version.c b/src/version.c
index 5cb09f8..f0107fa 100644
--- a/src/version.c
+++ b/src/version.c
@@ -742,6 +742,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    597,
+/**/
     596,
 /**/
     595,