do-edit-operation in snip%

See do-edit-operation.

Called when the snip's editor's method is called, recursive? is not #f, and this snip owns the caret.

• (send a-snip do-edit-operation op recursive? time) -> void
     op : symbol in '(undo redo clear cut copy paste kill select-all insert-text-box insert-pasteboard-box insert-image)
   recursive? = #t : boolean
     time = 0 : exact integer

  See do-edit-operation in editor<%> for information about the arguments.