[perl #114864] Make UNIVERSAL::DESTROY changes invalidate caches

[perl #114864] Make UNIVERSAL::DESTROY changes invalidate caches

Commit 8c34e50d inadvertently caused DESTROY caches not to be
reset when UNIVERSAL::DESTROY changes.  Normally, a change to
a method will cause mro_method_changed_in to be called on all
subclasses, but mro.c cheats for UNIVERSAL and just does
++PL_sub_generation.  So clearing the DESTROY cache explicitly
in mro_method_changed_in is clearly not enough.