patch 8.0.0157: no completion for :syntax spell and :syntax sync

Problem:    No command line completion for ":syntax spell" and ":syntax sync".
Solution:   Implement the completion. (Dominique Pelle)
diff --git a/src/version.c b/src/version.c
index 350b4ad..824a292 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    157,
+/**/
     156,
 /**/
     155,