vim-patch:8.0.0069

Problem:    Compiler warning for self-comparison.
Solution:   Define ONE_WINDOW and add vim/vim#ifdef.

a1f4cb93ba

src/nvim/buffer.c

@@ -4429,7 +4429,7 @@ do_arg_all (
             }
           }
           /* don't close last window */
-          if (firstwin == lastwin
+          if (ONE_WINDOW
               && (first_tabpage->tp_next == NULL || !had_tab))
             use_firstwin = TRUE;
           else {