patch 9.0.0237: Mac: cannot build if dispatch.h is not available

Problem:    Mac: cannot build if dispatch.h is not available.
Solution:   Add #ifdef. (Evan Miller, closes #10954)
diff --git a/src/version.c b/src/version.c
index c12d3c9..3788596 100644
--- a/src/version.c
+++ b/src/version.c
@@ -732,6 +732,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    237,
+/**/
     236,
 /**/
     235,