Patch #5884.

(ll_for_each_reverse): New macro.
(ll_for_each_reverse_continue): New macro.
(ll_for_each_reverse_safe): New macro.
(ll_for_each_safe_reverse_continue): New macro.
(ll_for_each_reverse_preremove): New macro.
(ll_for_each_reverse_postremove): New macro.
(ll_remove__): Removed (dead code).
(ll_tail__): New macro.
(ll_prev__): New macro.