DEC - Decrement


	Usage:	DEC	dest
	Modifies flags: AF OF PF SF ZF


	Unsigned binary subtraction of one from the destination.


				 Clocks			Size
	Operands	 808x  286   386   486		Bytes

	reg8		  3	2     2	    1		  2
	mem		15+EA	7     6	    3		 2-4
	reg16/32	  3	2     2	    1		  1


	- see Instruction Timing