[css-display] Add note about root inline overriding anonymous inline from 2.1. Fixes #1383.

Author: tabatkins

css-display/Overview.bs

@@ -829,12 +829,15 @@ Appendix A: Glossary</h2>
 			or contains only block-level boxes
 			participating in a <a>block formatting context</a>
 			(possibly generating anonymous block boxes to ensure this constraint,
-			as defined in <a href="https://www.w3.org/TR/CSS2/visuren.html#anonymous-block-level">CSS2.1&sect;9.2.1.1</a>).
+			as defined in <a href="https://www.w3.org/TR/CSS2/visuren.html#anonymous-block-level">CSS2&sect;9.2.1.1</a>).
 
 			A block container that contains only inline-level content
 			establishes a new <a>inline formatting context</a>.
 			The element then also generates a <a>root inline box</a>
 			which wraps all of its inline content.
+			<span class=note>Note, this <a>root inline box</a> concept
+			effectively replaces the "anonymous inline element" concept
+			introduced in <a href="https://www.w3.org/TR/CSS2/visuren.html#anonymous">CSS2&sect;9.2.2.1</a>.</span>
 
 			A block container that contains only block-level boxes
 			establishes a new <a>block formatting context</a>