"This memorandum provides direction ... on the application of the accrued benefit rules under section 411(b)(1)(G) of the Internal Revenue Code to pending requests for determination letters by [pension equity plans (PEPs)].... [A] PEP must contain language that ensures compliance with the accrued benefit rules under section 411(b)(1)(G). Pending the issuance of guidance that will provide for more specific ways of complying with section 411(b)(1)(G), this directive contains a number of acceptable provisions for inclusion in plan documents."