set-filename in editor:file-mixin

Set the path name for the file to be saved from or reloaded into this editor. This method is also called when the filename changes through any method (such as load-file).

• (send an-editor:file-mixin set-filename name temp? void
     name : string
     temp? = #f : boolean

  Updates the filename on each frame displaying this editor, for each frame that matches frame:editor<%>.