cssFloat is only accessible as styleFloat on IE8

#1841
Updated, better? We could use a map instead, which could also do double-duty for discarding valid but invalid style names (`cssFloat`, `styleFloat`, etc).

Also, would you mind sticking the shorthandPropertyExpansions behind `document.documentMode < 9 ? AFAIK this only targets IE8, so it would make sense as we could squeeze "quite alot" more performance out of it for all other browsers. (Separate PR though, ofc)