patch 8.0.1485: weird autocmd may cause arglist to be changed recursively

Problem:    Weird autocmd may cause arglist to be changed recursively.
Solution:   Prevent recursively changing the argument list. (Christian
            Brabandt, closes #2472)

src/ex_docmd.c

@@ -8058,6 +8058,16 @@ alist_set(
     int		fnum_len)
 {
     int		i;
+    static int  recursive = 0;
+
+    if (recursive)
+    {
+#ifdef FEAT_AUTOCMD
+	EMSG(_(e_au_recursive));
+#endif
+	return;
+    }
+    ++recursive;
 
     alist_clear(al);
     if (ga_grow(&al->al_ga, count) == OK)
@@ -8087,6 +8097,8 @@ alist_set(
 	FreeWild(count, files);
     if (al == &global_alist)
 	arg_had_last = FALSE;
+
+    --recursive;
 }
 
 /*