"A" magic is gone. The changes to the handling of the C<SVf_AMAGIC> flag
eliminate the need for it.
-The core no longer increments C<PL_amagic_generation> (it doesn't need to).
-But an XS module can still increment it to mark all overload tables as
-stale. (It is still not part of the API, though.) Do not rely on this.
-It may be deleted in the next release.
+C<PL_amagic_generation> has been removed as no longer necessary. For XS
+modules, it is now a macro alias to C<PL_na>.
The fallback overload setting is now stored in its own stash entry, called
"(fallback".