patch 9.0.1390: FOR_ALL_ macros are defined in an unexpected file

Problem:    FOR_ALL_ macros are defined in an unexpected file.
Solution:   Move FOR_ALL_ macros to macros.h.  Add FOR_ALL_HASHTAB_ITEMS.
            (Yegappan Lakshmanan, closes #12109)

src/window.c

@@ -5622,7 +5622,7 @@ win_free(
 		// If there already is an entry with "wi_win" set to NULL it
 		// must be removed, it would never be used.
 		// Skip "wip" itself, otherwise Coverity complains.
-		for (wip2 = buf->b_wininfo; wip2 != NULL; wip2 = wip2->wi_next)
+		FOR_ALL_BUF_WININFO(buf, wip2)
 		    if (wip2 != wip && wip2->wi_win == NULL)
 		    {
 			if (wip2->wi_next != NULL)
@@ -7378,7 +7378,7 @@ reset_lnums(void)
 
 /*
  * A snapshot of the window sizes, to restore them after closing the help
- * window.
+ * or other window.
  * Only these fields are used:
  * fr_layout
  * fr_width
@@ -7390,6 +7390,7 @@ reset_lnums(void)
 
 /*
  * Create a snapshot of the current frame sizes.
+ * "idx" is SNAP_HELP_IDX or SNAP_AUCMD_IDX.
  */
     void
 make_snapshot(int idx)
@@ -7473,6 +7474,7 @@ get_snapshot_curwin(int idx)
  * Restore a previously created snapshot, if there is any.
  * This is only done if the screen size didn't change and the window layout is
  * still the same.
+ * "idx" is SNAP_HELP_IDX or SNAP_AUCMD_IDX.
  */
     void
 restore_snapshot(