changed behaviour of malloc(0) and optimized calloc

[ZERICO2005]

calloc (when __TICE__ is defined) now uses an inlined implementation of bzero which uses the $E40000 address to speed up the zero filling of memory.

Otherwise, it will use the previous memset implementation when __TICE__ is undefined.

[ZERICO2005]

I assume it is okay for cpd to read nonnull_ptr_from_malloc + size

[ZERICO2005]

To reduce the complexity of this PR, I undid the allocator switches to nonzero_fill_calloc when malloc(0) is known to return NULL commits for now (which essentially added 4 different calloc variants). That way we can focus on the two important changes that will be made in this PR:

• Changing the behavior of __simple_malloc(0) and __standard_malloc(0) to return NULL.
• Optimizing calloc zero filling by using the $E40000 all zeros address

[runer112]

I believe that this should use calc84maniac's correction to be safe. Also, I suggest removing the reference to the TI-CE, as it's not really relevant to the assumption.

Suggested change

	; test for NULL
	add hl, bc
	; or a, a ; assumes that ptr + size does not overflow on TICE
	sbc hl, bc
	pop bc ; BC = size
	pop bc ; BC = size
	; test for NULL
	add hl, bc
	; or a, a ; assumes that ptr + size does not overflow
	sbc hl, bc