* alloc.c (make_pure_float): Align pureptr on a sizeof (double)

* alloc.c (make_pure_float): Align pureptr on a sizeof (double)
	boundary before allocating the float.

	* alloc.c: Add description lines to the top of each page.

	* alloc.c (mark_interval_tree): Remove spurious & in front of
	function name.

	* alloc.c (UNMARK_BALANCE_INTERVALS): Fix to accomodate compilers
	other than GCC, which do not allow casts on the LHS of an
	assignment.

	* alloc.c (mark_object, mark_buffer): Remove some unused
	variables.