Make the compiler aware that `add\sub\and\or\xor` etc can be used on memory operands

[ZERICO2005]

; current
	ld	iy, (ix - 6)
	ld	a, (iy)
	ld	l, (ix - 12)
	and	a, l
;	ld	l, a ; L is unused
	ld	c, (ix - 20)
;	ld	a, l ; redundant
	or	a, c
	ld	l, a
	ld	(iy), l
	lea	hl, iy + 0
	ld	bc, (ix - 15)
	add	hl, bc
	ld	a, (hl)
	push	de
	pop	bc

; optimal
	ld	iy, (ix - 6)
	ld	a, (iy)
	and	a, (ix - 12)
	or	a, (ix - 20)
	ld	(iy), a
	lea	hl, iy + 0
	ld	bc, (ix - 15)
	add	hl, bc
	ld	a, (hl)
	push	de
	pop	bc