CWDE - Convert Word to Extended Doubleword (386+ only)

	Usage:	CWDE
	Modifies flags: None


	Converts a signed word in AX to a signed doubleword in EAX by
	extending the sign bit of AX throughout EAX.

				 Clocks			Size
	Operands	 808x  286   386   486		Bytes

	none		  -	-     3	    3		  1


	- see Instruction Timing