Adds type handler
@param {*} cls
@param {Function} replacer
@param {Function} reviver
function addHandler(cls, replacer, reviver) {
	if (typeof cls !== "function") {
		throw new TypeError("'cls' must be class/function");
	}
	if (typeof replacer !== "function") {
		throw new TypeError("'replacer' must be function");
	}
	if (typeof reviver !== "function") {
		throw new TypeError("'reviver' must be function");
	}
	__handlers[cls.name] = {
		cls: cls,
		replacer: replacer,
		reviver: reviver
	};
}