Simplify `use VERSION behaviour` on 5.37 onwards

[leonerd]

(this description was all wrong but in any case I've now reverted it to a draft. We'll wait for 5.39 to apply it properly. I'll write something better by then)

[Leont]

There are two «if (shortver >= SHORTVER(5, 35))»s in there, can't they be merged?

[leonerd]

There are two «if (shortver >= SHORTVER(5, 35))»s in there, can't they be merged?

They could, but that might make the logic harder to read. At the moment, there's a clear split between "fiddling with strict bits", followed by "apply warnings".

[leonerd]

Actually this doesn't fix any back-compat. It just adds new behaviour. Probably best to save it for .39 after all.

[jkeenan]

@leonerd, this p.r. now has merge conflicts. Do you want to resolve those -- or would it be better to start fresh with a new p.r.?

[leonerd]

Resolved conflicts and repushed; retargeted for 5.39 instead.

[jkeenan]

@leonerd, this pull request has been in draft status for 12 months and has merge conflicts for 6 months. If you intend to move forward with it, could you resolve conflicts, remove the draft status and re-push? Thanks.