patch 9.0.0684: skipped :exe command fails compilation on MS-Windows

Problem:    Skipped :exe command fails compilation on MS-Windows.
Solution:   Adjust return value when skipping.
diff --git a/src/version.c b/src/version.c
index 8be8b38..953bb22 100644
--- a/src/version.c
+++ b/src/version.c
@@ -700,6 +700,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    684,
+/**/
     683,
 /**/
     682,