[css-images] Swap order of round/mod for image-orientation, so you get consistent answers for same angle.

Author: tabatkins

css-images/Overview.bs

@@ -1502,11 +1502,11 @@ Orienting an Image on the Page: the 'image-orientation' property {#the-image-ori
 			(in a clockwise direction),
 			while negative values cause a rotation to the left.
 			The computed value of the property is calculated
-			by rounding the specified angle to the nearest quarter-turn
-			(90deg, 100grad, .25turn, etc.),
+			by moduloing the value by ''1turn''
+			(so that it lies in the half-open range [''0turn'', ''1turn'')),
+			then rounding it to the nearest quarter-turn,
 			rounding away from 0
-			(that is, 45deg is rounded  to 90deg, while -45deg is rounded to -90deg),
-			then moduloing the value by 1 turn (360deg, 400grad, etc.).
+			(so ''45deg'' rounds to ''90deg'', etc).
 
 		<>? flip