d: Use new isTypeXxxx helpers where possible.

d: Use new isTypeXxxx helpers where possible.

gcc/d/ChangeLog:

	* d-builtins.cc (d_eval_constant_expression): Use isTypeXxxx helpers
	instead of explicit casts.
	(d_build_builtins_module): Likewise.
	* d-codegen.cc (get_array_length): Likewise.
	(identity_compare_p): Likewise.
	(lower_struct_comparison): Likewise.
	(build_array_from_val): Likewise.
	(array_bounds_check): Likewise.
	(get_function_type): Likewise.
	(d_build_call): Likewise.
	* d-compiler.cc (Compiler::paintAsType): Likewise.
	* d-convert.cc (convert_expr): Likewise.
	(convert_for_assignment): Likewise.
	* d-lang.cc (d_classify_record): Likewise.
	(d_build_eh_runtime_type): Likewise.
	* decl.cc (DeclVisitor::visit): Likewise.
	* expr.cc (ExprVisitor::needs_postblit): Likewise.
	(ExprVisitor::needs_dtor): Likewise.
	(ExprVisitor::visit): Likewise.
	* imports.cc (ImportVisitor::visit): Likewise.
	* typeinfo.cc (get_typeinfo_kind): Likewise.
	(TypeInfoVisitor::visit): Likewise.
	(TypeDeclInfoVisitor::visit): Likewise.
	* types.cc (merge_aggregate_types): Likewise.
	(TypeVisitor::visit): Likewise.