patch 7.4.1557
Problem:    Windows cannot be identified.
Solution:   Add a unique window number to each window and functions to use it.
diff --git a/src/version.c b/src/version.c
index 9c15aaf..bed7a46 100644
--- a/src/version.c
+++ b/src/version.c
@@ -744,6 +744,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1557,
+/**/
     1556,
 /**/
     1555,