tr.rdf doesn't include versionless URLs consistently

Denis—I hope you're the right person to contact about this; if not, please
forward it on!

For example, we have in tr.rdf:

@prefix doc: <http://www.w3.org/2000/10/swap/pim/doc#> .
@prefix rec53: <http://www.w3.org/2001/02pd/rec54#> .

<https://www.w3.org/TR/2017/WD-webrtc-20170605/>
  doc:versionOf <https://www.w3.org/TR/webrtc/>
.

But we don't have:

<http://www.w3.org/TR/2016/CR-css-flexbox-1-20160526/>
  doc:versionOf <http://www.w3.org/TR/css-flexbox/>
.

Given loading <https://www.w3.org/TR/css-flexbox/> gives the same resource
as <http://www.w3.org/TR/2016/CR-css-flexbox-1-20160526/>, I'd have
expected it to have appeared in  tr.rdf. (Indeed, I'd expect all current
resolvable URLs in /TR/ to appear in tr.rdf. And ideally we'd have some
historic archive of all resolvable URLs in /TR/ somewhere.)

Note we also don't have:

<http://www.w3.org/TR/2016/CR-css-flexbox-1-20160526/>
  rec54:sameWorkAs <https://www.w3.org/TR/2016/CR-css-flexbox-1-20160526/>
.

And I'd expect that given nowadays it redirects to it (at least if the
client sends Upgrade-Insecure-Requests: 1).

/Geoffrey