can-do-edit-operation? in editor<%>

Checks whether a generic edit command would succeed for the editor. This check is especially useful for enabling and disabling menus on demand.

• (send an-editor can-do-edit-operation? op recursive?) -> boolean
     op : symbol in '(undo redo clear cut copy paste kill select-all insert-text-box insert-pasteboard-box insert-image)
   recursive? = #t : boolean

  See do-edit-operation for information about the op and recursive? arguments.