Remove multi-line macros (ITERATE_DL_HASHTBL_*) in finalize

Remove multi-line macros (ITERATE_DL_HASHTBL_*) in finalize
(code refactoring)

* finalize.c (ITERATE_DL_HASHTBL_BEGIN, ITERATE_DL_HASHTBL_END,
DELETE_DL_HASHTBL_ENTRY): Remove macro.
* finalize.c (GC_make_disappearing_links_disappear): Add
is_remove_dangling argument (true means removal of dangling disappearing
links, false means make the disappearing links disappear); rename curr
and next local variables to curr_dl and next_dl, respectively; expand
ITERATE_DL_HASHTBL_BEGIN, DELETE_DL_HASHTBL_ENTRY and
ITERATE_DL_HASHTBL_END macros; remove real_ptr local variable; reformat
code.
* finalize.c (GC_remove_dangling_disappearing_links): Remove.