[css-overflow] Move overflow framgents to an appendix

See w3c#8271

Author: frivoal

css-overflow-4/Overview.bs

@@ -690,10 +690,16 @@ If there is insufficient space for both start
 and end ellipses/strings,
 then only the end ellipsis/string should be rendered.
 
-<h2 id="fragmentation">
-Redirection of Overflow</h2>
+<h2 id="fragmentation" no-num>
+Appendix A: Redirection of Overflow</h2>
 
 	ISSUE: This section is highly experimental.
+	It documents current attempts
+	at extending the capabilities of the 'continue' property
+	to solve additional use cases.
+	However, it does not currently have consensus.
+	It is presented here to encourage discussion,
+	but non-experimental implementation is not recommended.
 
 	<p>
 		In CSS Level 1 [[CSS1]], placing more content than would fit
@@ -1408,7 +1414,7 @@ that effect.
 	</div>
 
 <h2 id=sbg-ext class=nonum>
-Appendix A: Possible extensions for ''scrollbar-gutter''</h2>
+Appendix B: Possible extensions for ''scrollbar-gutter''</h2>
 
 <i>This section is non-normative.</i>
 
@@ -1778,12 +1784,12 @@ showing in which case space is reserved for the <a>scrollbar gutter</a>.
 </div>
 
 <h2 id=privclass=nonum>
-Appendix B: Privacy Considerations</h2>
+Appendix C: Privacy Considerations</h2>
 
 This specification introduces no new privacy considerations.
 
 <h2 id=sec class=nonum>
-Appendix B: Security Considerations</h2>
+Appendix D: Security Considerations</h2>
 
 This specification introduces no new security considerations.