INT B3 - ZIPKEY - RESTORE ZIPKEY CONTEXT                                        
	AH = 7Ch
	BL = maximum number of characters for a city name
	BH = ZIPKEY state code for last city-name search, or FFh if none
	CX:DX = internal code returned by AH=7Bh
Return: CF set on error
	CF clear if successful
	AX destroyed
SeeAlso: AH=7Bh