Change type of hb_sz field (of hblkhdr) from size_t to word

Change type of hb_sz field (of hblkhdr) from size_t to word

This is needed to make the size of hb_sz to be the same as of AO_t.

* allchblk.c [USE_MUNMAP] (GC_unmap_old): Cast hhdr->hb_sz to size_t
when passed to GC_unmap().
* allchblk.c (GC_allochblk_nth): Cast hhdr->hb_sz to signed_word when
assigned to size_avail.
* allchblk.c [USE_MUNMAP] (GC_allochblk_nth): Cast hhdr->hb_sz to
size_t when passed to GC_remap().
* alloc.c (GC_set_fl_marks, GC_clear_fl_marks): Change type of sz and
bit_no local variables from size_t/unsigned to word.
* dbg_mlc.c (GC_check_heap_block): Likewise.
* backgraph.c [MAKE_BACK_GRAPH] (per_object_helper): Cast hhdr->hb_sz
to size_t; change type of i local variables from int to size_t.
* checksums.c [CHECKSUMS] (GC_on_free_list): Change type of sz local
variable from size_t to word.
* mark.c (GC_push_marked, GC_push_unconditionally, GC_block_was_dirty):
Likewise.
* reclaim.c (GC_reclaim_small_nonempty_block,
GC_disclaim_and_reclaim_or_free_small_block, GC_reclaim_block,
GC_n_set_marks): Likewise.
* checksums.c [CHECKSUMS] (GC_add_block): Remove bytes local variable
(to avoid casting of hhdr->hb_sz).
* dbg_mlc.c (GC_debug_free): Change type of i and obj_sz local
variables from size_t to word.
* dbg_mlc.c (GC_check_leaked): Likewise.
* extra/pcr_interface.c (GC_enumerate_block): Change type of sz local
variable from int to size_t.
* extra/pcr_interface.c (GC_enumerate_block): Cast hhdr->hb_sz to
size_t when assigned to sz.
* mallocx.c (GC_realloc): Likewise.
* mark.c (GC_set_hdr_marks): Likewise.
* reclaim.c (GC_do_enumerate_reachable_objects): Likewise.
* include/private/gc_pmark.h [MARK_BIT_PER_OBJ] (PUSH_CONTENTS_HDR):
Cast hhdr->hb_sz to size_t in assignment of obj_displ.
* include/private/gc_priv.h (struct hblkhdr): Change type of hb_sz from
size_t to word.
* include/private/gc_priv.h (MARK_BIT_NO): Cast offset argument to word
instead of unsigned.
* malloc.c (GC_free): Cast hhdr->hb_sz to size_t.
* mallocx.c (GC_get_kind_and_size): Likewise.
* mark.c (GC_clear_hdr_marks): Likewise.
* misc.c (GC_size): Likewise.
* misc.c (GC_do_blocking): Remove redundant cast of hhdr->hb_sz.
* reclaim.c (GC_reclaim_clear, GC_reclaim_uninit,
GC_disclaim_and_reclaim, GC_continue_reclaim): Change type of sz
argument from size_t to word.
* typd_mlc.c (GC_array_mark_proc): Change type of sz and nwords local
variables from size_t to word.