===PIC Z80-like DI and EI macros to Disable and Enable interrupts (globally)===

Globally disable/enable all interrupts.  This is fairly blunt and if you are looking to stop only a certain interrupt this isn't for you - you'll still have to hand-crank that.

Note that we check the interrupts have actually been disabled. Internals of the PIC mean it might take a few cycles to happen so we just circle (a few times max) until GIE clears.

<code>

	; disable global irq
DI 	MACRO
		BCF	INTCON,GIE		; disable global interrupt
		BTFSC	INTCON,GIE		; check if disabled... might take a few cycles to settle - can't assume
		GOTO	$-2			; nope, try again
	ENDM

	; enable global irq
EI	MACRO
		BSF	INTCON,GIE		; enable global interrupt
	ENDM

</code>