patch 8.0.0690: compiler warning on non-Unix system

Problem:    Compiler warning on non-Unix system.
Solution:   Add #ifdef. (John Marriott)
diff --git a/src/version.c b/src/version.c
index 64f035d..27f0436 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    690,
+/**/
     689,
 /**/
     688,