Text pointer being walked. FollowLinkPointer_CopyLink and ReadPointerFirstDisplay also store the word from B868 here. Used by AADB, AB03, AB0E, ReadObjectProcessingFlag, AB6F, AB83, ACDC, ApplySavedClause_RestoreWord, SaveTextPointer, SaveTextPointer_RecordObjectProcessing, B06D, FollowLinkPointer_CopyLink, ReadPointerFirstDisplay, ReadPointerFirstDisplay_ObjectProcessingSource, D788 and D797.