Implement P0722R3, destroying operator delete.

Implement P0722R3, destroying operator delete.

A destroying operator delete takes responsibility for calling the destructor
for the object it is deleting; this is intended to be useful for sized
delete of a class allocated with a trailing buffer, where the compiler can't
know the size of the allocation, and so would pass the wrong size to the
non-destroying sized operator delete.

gcc/c-family/
	* c-cppbuiltin.c (c_cpp_builtins): Define
	__cpp_impl_destroying_delete.
gcc/cp/
	* call.c (std_destroying_delete_t_p, destroying_delete_p): New.
	(aligned_deallocation_fn_p, usual_deallocation_fn_p): Use
	destroying_delete_p.
	(build_op_delete_call): Handle destroying delete.
	* decl2.c (coerce_delete_type): Handle destroying delete.
	* init.c (build_delete): Don't call dtor with destroying delete.
	* optimize.c (build_delete_destructor_body): Likewise.
libstdc++-v3/
	* libsupc++/new (std::destroying_delete_t): New.

From-SVN: r266053