Completing the work on a deinit pass and OENTRY field brought up another question.
Since we removed the k- and a- function difference, the relevance of the thread field in OENTRY has disappeared. 

It was only used in setting up the processing lists (instance() in insert.c), and is now so simple that we may just
as well check for the presence of the functions. In fact that’s what I have done in the PR.

The question is: should we just remove it? In the PR it’s basically non-op.
If we are not removing it, I can restore the (limited) use we had before.

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Prof. Victor Lazzarini
Maynooth University
Ireland