patch 9.0.0290: compiler warning for variable set but not used

Problem:    Compiler warning for variable set but not used.
Solution:   Add #ifdef.
diff --git a/src/version.c b/src/version.c
index 32c132c..35df02c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -708,6 +708,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    290,
+/**/
     289,
 /**/
     288,