Used internally to get value either raw or wrapped as specified by the `wrapItems` flag.
@param key {*}
@param value {*}
@param priority {Number}
@method sjl.stdlib.PriorityList#resolveItemWrapping
@returns {*|PriorityListItem}
function (key, value, priority) {
            var normalizedPriority = this.normalizePriority(priority),
                serial = this._internalSerialNumbers++;
            if (this.wrapItems) {
                return new (this.itemWrapperConstructor) (key, value, normalizedPriority, serial);
            }
            try {
                value.key = key;
                value.priority = priority;
                value.serial = serial;
            }
            catch (e) {
                throw new TypeError('PriorityList can only work in "unwrapped" mode with values/objects' +
                    ' that can have properties created/set on them.  Type encountered: `' + sjl.classOf(value) + '`;' +
                    '  Original error: ' + e.message);
            }
            return value;
        }