altText and hoverText Icon attributes missing from VAST 4.2 XSD

[YoTonyF]

The altText and hoverText attributes for an <Icon> element (which were added in some version of VAST 4.2) are not declared in the vast 4.2 XSD document (inside the "Icon_type" definition)

Note that I'm not referring to the <AltText> node beneath <IconClickFallbackImage> which IS included, I'm only referring to the attribute(s) of the <Icon> node.