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)

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    157,
 /**/
     156,
 /**/