updated for version 7.4.312

Problem:    Cannot figure out what argument list is being used for a window.
Solution:   Add the arglistid() function. (Marcin Szamotulski)

src/ex_docmd.c

@@ -7211,6 +7211,7 @@ alist_new()
     else
     {
 	curwin->w_alist->al_refcount = 1;
+	curwin->w_alist->id = ++max_alist_id;
 	alist_init(curwin->w_alist);
     }
 }