Fix DoCon: Another try at getting extractResults right

Fix DoCon: Another try at getting extractResults right

For some reason TcSimplify.extractResults is quite difficult to get right.
This is another attempt; finally I think I have it.

Strangely enough, it's only Sergey's DoCon program that shows up the
bug, which manifested as a failure in the Simplifier

        lookupRecBndr $dGCDRing{v a1Lz} [lid]

But it was due to extractResults producing multiple bindings for
the same dictionary.

Please merge this to the stable branch (after previous patches to
TcSimplify though).