(check_memory_limits): Reduce warnlevel when usage drops far enough.

(check_memory_limits): Reduce warnlevel when usage drops far enough.

(memory_warnings): New function; just set warning data.
Use start_of_data if start is 0.

[!emacs]: Don't include config.h or lisp.h;
instead, use stddef.h.  Define POINTER, SIZE, EXCEEDS_LISP_PTR.

[!emacs] (safe_bcopy): Define as macro using memmove.
(r_alloc_free): Clear *ptr.
(r_alloc_init): Renamed from malloc_init.  Take no args.
Make it static; declare at top of file.
(r_alloc): Call r_alloc_init, if not initialized yet.
(r_alloc_initialized): Renamed from malloc_initialized; moved to top.
(ROUNDUP): Subtract 1, in case arg is already aligned.

(check_memory_limits): EXCEEDS_LISP_PTR renamed from EXCEEDS_ELISP_PTR.