c++: no clobber for C++20 destroying delete [PR91859]

c++: no clobber for C++20 destroying delete [PR91859]

Before C++20 added destroying operator delete, by the time we called
operator delete for a pointer, the object would already be gone.  But that
isn't true for destroying delete.  Since the optimizers' assumptions about
operator delete are based on either DECL_IS_REPLACEABLE_OPERATOR (which
already is not set) or CALL_FROM_NEW_OR_DELETE_P, let's avoid setting the
latter flag in this case.

	PR c++/91859

gcc/ChangeLog:

	* tree.h (CALL_FROM_NEW_OR_DELETE_P): Adjust comment.

gcc/cp/ChangeLog:

	* call.c (build_op_delete_call): Don't set CALL_FROM_NEW_OR_DELETE_P
	for destroying delete.
	* init.c (build_delete): Don't clobber before destroying delete.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/destroying-delete5.C: New test.