[perl #73618] no-iteration until loop incorrectly optimised away

Fixed in 317f3b6, but only for the case of 'while', not the case of
'until'. Fixing 'until' is harder because the parser itself rewrites
"until (1)" to "while (!1)" directly, and so "!1" is constant-folded to
'' before the while loop is even constructed. I'll leave this open (with
an updated title) in the hopes that someone else feels like fixing that
aspect of it (I left a TODO test in t/op/loopctl.t).

-doy

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via perlbug:  queue: perl5 status: open
https://rt.perl.org:443/rt3/Ticket/Display.html?id=73618

• [perl #73618] no-iteration until loop incorrectly optimised away by Jesse Luehrs via RT