c++: use _P() defines from tree.h

c++: use _P() defines from tree.h

gcc/cp/ChangeLog:

	* call.cc (promoted_arithmetic_type_p): Use _P defines from tree.h.
	(build_conditional_expr): Ditto.
	(convert_like_internal): Ditto.
	(convert_arg_to_ellipsis): Ditto.
	(build_over_call): Ditto.
	(compare_ics): Ditto.
	* class.cc (is_empty_base_ref): Ditto.
	* coroutines.cc (rewrite_param_uses): Ditto.
	* cp-tree.h (DECL_DISCRIMINATOR_P): Ditto.
	(ARITHMETIC_TYPE_P): Ditto.
	* cvt.cc (ocp_convert): Ditto.
	* cxx-pretty-print.cc (pp_cxx_template_argument_list): Ditto.
	* decl.cc (layout_var_decl): Ditto.
	(get_tuple_size): Ditto.
	* error.cc (dump_simple_decl): Ditto.
	* lambda.cc (start_lambda_scope): Ditto.
	* mangle.cc (write_template_arg): Ditto.
	* method.cc (spaceship_comp_cat): Ditto.
	* module.cc (node_template_info): Ditto.
	(trees_out::start): Ditto.
	(trees_out::decl_node): Ditto.
	(trees_in::read_var_def): Ditto.
	(set_instantiating_module): Ditto.
	* name-lookup.cc (maybe_record_mergeable_decl): Ditto.
	(consider_decl): Ditto.
	(maybe_add_fuzzy_decl): Ditto.
	* pt.cc (convert_nontype_argument): Ditto.
	* semantics.cc (handle_omp_array_sections_1): Ditto.
	(finish_omp_clauses): Ditto.
	(finish_omp_target_clauses_r): Ditto.
	(is_this_parameter): Ditto.
	* tree.cc (build_cplus_array_type): Ditto.
	(is_this_expression): Ditto.
	* typeck.cc (do_warn_enum_conversions): Ditto.
	* typeck2.cc (store_init_value): Ditto.
	(check_narrowing): Ditto.