Revert "Re: [perl #51636] segmentation fault with array ties"

Revert "Re: [perl #51636] segmentation fault with array ties"

This reverts commit 90630e3c741716305d7f1da4df5eab5c1bee42cc.

This fix turns out to be wrong, and also made ($<,$>)=(...) fail
(RT #75212).

The original problem was a SEGV in av_clear(). This was mis-diagnosed
as recursive PL_delaymagic issue, and the fix was to temprarily reset
PL_delaymagic to zero. This stopped the mg_set() of $> and $> being
delayed.

The real problem was that mg_free wasn't clearing the [GSR]MG flags
after freeing xmg_magic. This was independently fixed by commit
68f8932eb570af656553ed44c11a23f0a216a3ec.