(ALIGN): Add casts to simplify usage.

(ALIGN): Add casts to simplify usage.
(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.