Notice of Filing and Immediate Effectiveness of Proposed Rule Change To Amend Rule 11.18 To Address the Exchange's Liability for System Failures; Amend Rule 2.11 To Provide for an Error Account Maintained by the Exchange's Routing Broker; Adopt Rule 11.11(e) To Allow Cancellation of Orders When a System Failure Occurs; Amend Rule 1.5 To Reposition the Definition of a Trading Center; and Make Other Non-Substantive and Conforming Changes