patch 8.2.0500: using the same loop in many places

Problem:    Using the same loop in many places.
Solution:   Define more FOR_ALL macros. (Yegappan Lakshmanan, closes #5339)
diff --git a/src/arglist.c b/src/arglist.c
index ad404d8..8e0f4d2 100644
--- a/src/arglist.c
+++ b/src/arglist.c
@@ -1046,7 +1046,7 @@
 	    // Move the already present window to below the current window
 	    if (curwin->w_arg_idx != i)
 	    {
-		for (wpnext = firstwin; wpnext != NULL; wpnext = wpnext->w_next)
+		FOR_ALL_WINDOWS(wpnext)
 		{
 		    if (wpnext->w_arg_idx == i)
 		    {