(unchain_overlay): New function.
(add_overlay_mod_hooklist): Use AREF.
(copy_overlays, reset_buffer, overlays_at, overlays_in)
(overlay_touches_p, overlay_strings, recenter_overlay_lists)
(fix_overlays_in_range, fix_overlays_before, Fmake_overlay)
(Fmove_overlay, Fdelete_overlay, Foverlay_lists)
(report_overlay_modification, evaporate_overlays, init_buffer_once):
Adjust to new type of overlays_(before|after).
(adjust_overlays_for_insert, adjust_overlays_for_delete)
(fix_overlays_in_range, Fmake_overlay, Fmove_overlay)
(evaporate_overlays, init_buffer_once): Update use of overlay_center.
(overlays_at, evaporate_overlays, recenter_overlay_lists)
(overlay_strings, fix_overlays_before): Use EMACS_INT for positions.
(BLOCK_ALIGN, BLOCK_BYTES, ABLOCKS_PADDING, ABLOCKS_SIZE)
(ABLOCKS_BYTES, ABLOCK_ABASE, ABLOCKS_BUSY, ABLOCKS_BASE): New macros.
(struct ablock, struct ablocks): New types.
(free_ablock): New global var.
(lisp_align_malloc, lisp_align_free): New functions.
(FLOAT_BLOCK_SIZE): Redefine in terms of BLOCK_BYTES.
(struct float_block): Reorder and add gcmarkbits.
(GETMARKBIT, SETMARKBIT, UNSETMARKBIT, FLOAT_BLOCK, FLOAT_INDEX)
(FLOAT_MARKED_P, FLOAT_MARK, FLOAT_UNMARK): New macros.
(init_float, make_float): Use lisp_align_malloc.
(free_float, live_float_p): Don't use `type' any more.
(make_float): Use FLOAT_UNMARK to access to mark bit.
(mark_maybe_object, mark_maybe_pointer, survives_gc_p):
Use FLOAT_MARKED_P to access the mark bit.
(pure_alloc): Simplify use of ALIGN.
(mark_object): Use FLOAT_MARK to access the mark bit.
(gc_sweep): Use new macros to access the float's mark bit.
(init_alloc_once): Init free_ablock.
(GC_STRING_BYTES): Don't mask markbit (it's only used on `size').
(allocate_buffer): Move.
(string_bytes): Don't mask markbit of `size_byte'.
(mark_maybe_object, mark_maybe_pointer, Fgarbage_collect)
(mark_object, mark_buffer, survives_gc_p, gc_sweep):
Use the `size' field of buffers (rather than the `name' field) for
the mark bit, as is done for all other vectorlike objects.
Use the new macros to access the mark bit of vectorlike objects.
