function _request(pool, Constructor) {
    return function request() {
        if (pool.length !== 0) return pool.pop();
        else return new Constructor();
    };
}
Register request and free functions for the given type.

@method register

@param {String} type             Unique object "type" to identity pools of
                                 allocated objects.
@param {Function} Constructor    Zero-argument Constructor function used for
                                 allocating new objects.
@return {undefined} undefined