Each eventspace has its own instance of snip-class-list<%>,
 obtained with (get-the-snip-class-list). New instances
 cannot be created directly. Each instance keeps a list of snip
 classes. This list is needed for loading snips from a file. See also
 Snip Classes.
| (send a-snip-class-list add snipclass) → void? | 
| snipclass : (is-a?/c snip-class%) | 
Adds a snip 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 class from the list with the given name, returning
 #f if none is found.
| (send a-snip-class-list find-position class) | 
| → exact-nonnegative-integer? | 
| class : (is-a?/c snip-class%) | 
Returns an index into the list for the specified class.
| (send a-snip-class-list nth n) | 
| → (or/c (is-a?/c snip-class%) false/c) | 
| n : exact-nonnegative-integer? | 
Returns the nth class in the list, or #f if
 the list has n classes or less.
| (send a-snip-class-list number) → exact-nonnegative-integer? | 
Returns the number of snip classes in the list.