patch 8.1.0239: now Ruby build fails on other systems

Problem:    Now Ruby build fails on other systems.
Solution:   Always define rb_intern. (Ken Takata, closes #3275)
diff --git a/src/version.c b/src/version.c
index c5f1812..bd8da20 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    239,
+/**/
     238,
 /**/
     237,