patch 9.0.0281: build failure without the +eval feature

Problem:    Build failure without the +eval feature.
Solution:   Add #ifdef.
diff --git a/src/version.c b/src/version.c
index 2247589..ae33d6d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -708,6 +708,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    281,
+/**/
     280,
 /**/
     279,