autosave:register in Framework Functions

• (autosave:register obj) -> void?
     obj : (and/c (is-a?/c autosave:autosavable<%>) (is-a?/c editor<%>))

  Adds obj to the list of objects to be autosaved. When it is time to autosave, the do-autosave method of the object is called. This method is responsible for performing the autosave.

  There is no need to de-register an object because the autosaver keeps a ``weak'' pointer to the object; i.e., the autosaver does not keep an object from garbage collection.