patch 8.0.0320: warning for unused variable with small build

Problem:    Warning for unused variable with small build.
Solution:   Change #ifdef to exclude FEAT_CMDWIN. (Kazunobu Kuriyama)
diff --git a/src/version.c b/src/version.c
index 09680b9..2d6940d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    320,
+/**/
     319,
 /**/
     318,