Each eventspace has an instance of editor-data-class-list<%>,
 obtained with (get-the-editor-data-class-list). New
 instances cannot be created directly. This list keeps a list of
 editor data classes; this list is needed for loading snips from a
 file. See also Editor Data.
| (send an-editor-data-class-list add snipclass) → void? | 
| snipclass : (is-a?/c editor-data-class%) | 
Adds a snip data class to the list. If a class with the same name already
exists in the list, this one will not be added.
Finds a snip data class from the list with the given name, returning
 #f if none can be found.
| (send an-editor-data-class-list find-position class) | 
| → exact-nonnegative-integer? | 
| class : (is-a?/c editor-data-class%) | 
Returns an index into the list for the specified class.
| (send an-editor-data-class-list nth n) | 
| → (or/c (is-a?/c editor-data-class%) false/c) | 
| n : exact-nonnegative-integer? | 
Returns the nth class in the list (counting from 0), returning
 #f if the list has n or less classes.
| (send an-editor-data-class-list number) | 
| → exact-nonnegative-integer? | 
Returns the number of editor data classes in the list.