updated for version 7.3.531
Problem:    GUI does not work on MS-Windows.
Solution:   Add the missing #ifdef. (Patrick Avery)
diff --git a/src/version.c b/src/version.c
index 5167379..ee34eb4 100644
--- a/src/version.c
+++ b/src/version.c
@@ -715,6 +715,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    531,
+/**/
     530,
 /**/
     529,