patch 8.0.0640: mismatch between help and actual message

Problem:    Mismatch between help and actual message for ":syn conceal".
Solution:   Change the message to match the help. (Ken Takata)

Author: brammool

src/syntax.c

@@ -3436,9 +3436,9 @@ syn_cmd_conceal(exarg_T *eap UNUSED, int syncing UNUSED)
     if (*arg == NUL)
     {
 	if (curwin->w_s->b_syn_conceal)
-	    MSG(_("syn conceal on"));
+	    MSG(_("syntax conceal on"));
 	else
-	    MSG(_("syn conceal off"));
+	    MSG(_("syntax conceal off"));
     }
     else if (STRNICMP(arg, "on", 2) == 0 && next - arg == 2)
 	curwin->w_s->b_syn_conceal = TRUE;

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    640,
 /**/
     639,
 /**/