*** describe sgml-save-options
Start-tags for undefined elements will either be ignored, if
sgml-ignore-undefined-elements is t, or assumed to be
acceptable in the current element and defined with O O ANY
Maximum number of characters used from the first and last entry of a sub-menu to indicate the range of that menu.
This is used for long menus of elements, tags or entities that are split
into sgml-max-menu-size big sub-menus.