[css-overflow-3] Add Previous Version link, and change Work Status from Exploring to Revising.

Author: dbaron

css-overflow-3/Overview.bs

@@ -1,12 +1,13 @@
 <h1>CSS Overflow Module Level 3</h1>
 <pre class="metadata">
 Status: ED
-Work Status: Exploring
+Work Status: Revising
 ED: https://drafts.csswg.org/css-overflow/
 Shortname: css-overflow
 Group: csswg
 Level: 3
 TR: https://www.w3.org/TR/css-overflow-3/
+Previous version: https://www.w3.org/TR/2016/WD-css-overflow-3-20160531/
 Previous version: https://www.w3.org/TR/2013/WD-css-overflow-3-20130418/
 Editor: L. David Baron, Mozilla, http://dbaron.org/
 Editor: Florian Rivoal, On behalf of Bloomberg, florian@rivoal.net, http://florian.rivoal.net/