*: use llist_pop for traverse-and-free list operation

function                                             old     new   delta
append_file_list_to_list                             109     111      +2
udhcpc_main                                         2414    2413      -1
run_parts_main                                       325     324      -1
od_main                                             2324    2323      -1
getopt_main                                          709     707      -2
env_main                                             253     251      -2
sed_main                                             659     656      -3
ps_main                                              522     519      -3
traceroute_main                                     3960    3954      -6
sort_main                                            844     838      -6
diff_main                                            866     858      -8
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/10 up/down: 2/-33)            Total: -31 bytes

diff --git a/editors/diff.c b/editors/diff.c
index 4e51f6f..26f3527 100644
--- a/editors/diff.c
+++ b/editors/diff.c
@@ -1289,14 +1289,9 @@
 	while (L_arg) {
 		if (label1 && label2)
 			bb_show_usage();
-		if (!label1)
-			label1 = L_arg->data;
-		else { /* then label2 is NULL */
+		if (label1) /* then label2 is NULL */
 			label2 = label1;
-			label1 = L_arg->data;
-		}
-		/* we leak L_arg here... */
-		L_arg = L_arg->link;
+		label1 = llist_pop(&L_arg);
 	}
 
 	/*