Fix &CORE::exit/die under vmsish "hushed"

Fix &CORE::exit/die under vmsish "hushed"

This commit makes them behave like exit and die without the ampersand
by moving the OPpHUSH_VMSISH hint from exit/die op to the current
statement (nextstate/cop) instead.  &CORE:: subs intentionally lack a
nextstate op, so they can see the hints in the caller’s nextstate op.