patch 8.2.0523: loops are repeated

Problem:    Loops are repeated.
Solution:   Use FOR_ALL_ macros. (Yegappan Lakshmanan, closes #5882)
diff --git a/src/evalwindow.c b/src/evalwindow.c
index ab4ba83..0db45bc 100644
--- a/src/evalwindow.c
+++ b/src/evalwindow.c
@@ -444,8 +444,7 @@
     l = list_alloc();
     if (l != NULL)
     {
-	for (wp = (tp == curtab) ? firstwin : tp->tp_firstwin;
-						   wp != NULL; wp = wp->w_next)
+	FOR_ALL_WINDOWS_IN_TAB(tp, wp)
 	    list_append_number(l, (varnumber_T)wp->w_id);
 	dict_add_list(dict, "windows", l);
     }